1. Your link does not support what you say: It points out a grand total of two lawsuits, and makes no particular argumentation that the taxi companies in those two cities are monopolies or oligopolies except in the sense that they are licensed.

2. I was not arguing about whether taxi companies could be construed as having some kind of monopoly, nor whether they are objectionable. I was correcting your broad strokes characterization of "how taxi licensing works."

Here is a chance for you to learn more about the world, rather than defending your mistaken perception. I am not attempting to make you like taxi companies more or less, or to support Uber more or less (I have fairly complicated views on both, and am by no means in anyone's camp). I am attempting to get you to understand how taxi licensing works, and also how regulatory capture works.

Taxi licensing is different in different cities. Substantially so! In some cases, medallions are given to individuals, in some cases they are given to corporations, in some cases they are given to both. There may be different classes of medallions that have different rights. Medallions may be traded or bought and sold. It is not the case in any major taxi market that I'm aware of that the principle way that medallions are granted is a single grant to a single company by an elected official. Which is not to say that it has never happened, since a lot of things have happened in this world.

Also, corruption of the straightforward "I give you money, you give me privileges" sort is probably (obviously it's hard to gather statistics) rare compared to regulatory capture via other means.

A TLC or similar agency probably has a mandate to do something like "promote the ability of residents and visitors of our city to get a safe, clean ride from point A to point B," and quite possibly other things like "provide a transportation infrastructure that disabled people can effectively use" or "be a revenue source" or whatever. Because taxi regulation is not (or was not in the pre-Uber era) a sexy exciting area of government, the chief people that a TLC bureaucrat (almost never a politician who is elected) will hear from in their attempts to satisfy the varying and sometimes conflicting natures of their mandates will be people in the local taxi industry. They'll end up doing a lot of negotiating, discussing, and horse-trading. In the course of this, it is inevitably the case that the bureaucrats regulating the taxi industry will understand and to some degree accept the worldview of the people they're regulating.

There will be lobbying, but rarely of the "I'll give you $1M for your wink campaign" variety. More of the, "This rule is hurting us badly, we need you to rescind it or to give us some other concession to make it bearable" variety. There will be corruption, but it does not involve the tuxedo'd owner of a giant monopoly bringing a slimy politician on a boozy weekend on the yacht. And while taxi companies may indeed close ranks to deal with an intrusive outsider such as Uber, they're (in the cities that I've seen most closely) anything but a cozy club.

None of this should be taken to mean that regulatory capture and corruption in the taxi business are unimportant. But solving the whole "regulators and regulatees work closely together" and "you have multiple mandates" problem is difficult, and trying a broad-strokes answer is unlikely to address the real local problems.