Rather than answer several individual posts, I'll be lazy and do a larger post which involves a lot of simplification and hand waving. I apologize in advance for any errors, but this seemed like a good way to handle insomnia instead of my normal lurking. If something is unclear or you think wrong, let me know.

Power Companies
circa 1900 there were lots of power companies, I've seen pictures of urban areas where there were multiple circuits run on poles, how many companies tried to serve a certain area, I do not know. Through lobbying investor owned utilities (IOU), or in most cases a single IOU gained the rights to serve an area exclusive. IOUs concentrated, for the most part, on serving dense load concentrations. As such the US Govt implemented the Rural Electrification Act, so low density areas could be served. The 2 types of electric utilities are public power (municipal, REA, RUS, PPD, UD, etc) and for profit (IOU's typically). In most cases, the IOUs give something to the government in exchange for the IOU providing service exclusively, it might be a tax or it might be free street lights. Municipals tend to subsidize the local government in some way, either through returned dollars or free power (street lights, buildings, traffic lights). IOUs typically have a defined rate of return and are supervised by a governing entity of some sort.

Vegetation Management
The recent SERC compliance meeting had a good presentation on vegetation management from the utility perspective and another on enforcement trends. In my opinion a lot of the issues in the W US is the result of the policy 'no fire is good', the sand pile game I think illustrates the issue where the longer sand keeps from falling results in a larger collapses (see Yellowstone fire). Since the late 1980's the issues with not burning has been known, I had an ecology class where if I recall correctly that was discussed for a couple of days. Tree trimming and clearing out undergrowth is done on a regular basis when the utility has an easement, but especially in urban areas folks tend to plant trees too close to power lines or even worse encroach on the easement with buildings. Most utilities patrol transmission lines at least once a year if not twice or monthly, sometimes this is aerial and other times it is feet on the ground walking the line. As an aside, the NESC governs clearance of electric lines to stuff and how stuff should be built; the RUS has publications on line design if you want to read about it.

Distribute Generation
The electric grid in the US is divided into 3 areas, Eastern Interconnect, Texas and Western Interconnect; they all function essentially the same. If I have a generator connected to the grid, it has to synchronize to the grid before closing the breaker. If it is done correctly then there is very little mechanical stress on the generator, if done incorrectly then there is a large amount of mechanical stress on the generator. One mis-operation I know about involved the A and B phases being swapped during a re-wind, when the generator was closed in at commissioning it had a large bang/clunk and the breaker opened immediately. The generator then had to be examined, i.e. taken back apart, to figure out what went wrong and if it could be put back into service.

If I have a generator partially supplying a facility (this can save a lot of money for an entity) and a fault happens on the grid then my goal is to protect the generator, so the generator will either shut off or island the facility while shedding load above the generator's capacity. This happens very quickly. One instance I know of, the urban area was supplied by transmission (aka remote generation), a 30 MW generator was the closest source, the utility had a fault because equipment misoperated and the generator was suddenly trying to supply all the power to that fault such that the generator protection operated and islanded the facility. It was no issue to close the grid interconnect back in (once it was ensured it was safe to do so) but the facility had to shed load to keep the generator running without causing electrical issues to load and damaging the generator.

Once a facility is islanded and running on its own generation the phase angle is a don't care until it is time to synchronize back to the grid. As long as the facility can shed load to maintain frequency (there is a NERC standard on Under Frequency Load Shed if you want to read about it) and not ruin equipment by having a power quality issue. During dynamic studies for system stability, it can be observed that a generator will diverge from the system frequency phase angle but not trip off because it is isolated from the grid which requires verification that isolation is happening and the protection scheme will indeed work that way on the actual system.

My observation is that most facilities, data centers and other processing facilities (refineries) tend to be the exception, concentrate on first costs when designing their electric infrastructure. It is possible to design a resilient system but it has a cost and it will not be utilized 100% until something goes wrong. And if you are doing research then that can be an issue as you may lose a large amount of data due to the power going out or possibly being sensitive to transients on the system, e.g. a switching operation on the transmission system affects the end user equipment. Even if you have redundant systems (and/or power supplies) it is possible to have single point of failures on your system. As well if you have enough local generation to supply your load, it may be more economical to not run 100% of your generation as the market price for electricity is cheaper than your cost of production (and there are folks who don't like idle assets, not realizing the greater benefit is not using it or only having to use it infrequently).

One other aspect of distributed generation is the automatic separation of the DG when loss of voltage is detected on the grid side. Utilities do not want voltage on their system if they have an outage due to worker safety (and other reasons). Utility crews in hurricane areas will typically investigate if they hear a generator running when the power is out to an area to ensure it is not back feeding the distribution line. As a reminder keep your feet together if you are near a downed power line and hop away, or even better don't go near downed power lines.