In CDR, Chip once commented that Fat Cat belonged in jail, so rodents must also have a penal system. We have no information on this point, but they must have a system of measurement all their own. Scientists, cooks, manufacturers, builders and tailors, to name a few, need to measure small quantities on a regular basis. Forget everything you've heard about mice living 3-5 years, their lifespans are similar to ours. The most definitve proof lies in Moustoria celebrating her Diamond Jubilee, commemorating 60 years as queen.
Mice employ a variety of methods of transportation.
In Mousetorian times, some mice worked as ostlers in conjunction with horses to direct the animals to stop at the appropriate places for their fares. Certain other forms of human's public transportaion also conceal a mouse crew. Most trains and ships have mice working aboard them and take on rodent passengers. In GMD, we see several books and newspapers, so mice do use printed materials. They also certainly have postal services.