SO far as I know they are USPS employees. Not sure of the details but there are IRS rules about using your vehicle for the job. The rural mail carriers I've talked to say the tax breaks and mileage makes up for the use of the private car.
You generally can either depreciate and expense all of your costs or claim a mileage rate for use. More record keeping for the depreciation and tracking expenses, but generally more favorable tax wise.
I am surprised it has taken this long to make this change. The big change if it is enacted is the next day first class mail delivery within a certain range going to two day. Essentially everything gets bumped one day longer. I don't believe this is included in the current proposal but it was previously.
The USPS is between a rock and hard place. They are a quasi governmental agency and subject to the whims of the legislature. If they are a government agency, then they should just be brought back to solvency just like all the other government agencies spending money. If they are a private business, they should be able to make their own business decisions.
I feel sure closing a bunch of small post offices in urban and rural areas will bug a lot of people, but the whole thing has gotten obese. The fat needs to be cut. The sooner it happens the better.
I for one have been using the USPS for my business stuff much more this year than the last few. I just can't justify spending $30 > $60 for a small package delivery any more when I only loose a single day in terms of delivery. I have already made changes to my project structure and if a customer wants next day delivery, they pay for it beyond the price I quote. My savings in January alone were over $300 and I am a very small business. FedEx misses my smiling face several times a week now.