It's a crapshoot. Best thing is to keep your own records, make sure you have copies of everything, and be meticulous about it all. Some companies will include gas payments and fees, some will include both of those and your reimbursements, some will just include the fee and no gas payments, and others will include some random hodgepodge of both that no amount of accounting can figure out exactly what is reported on that 1099 -_-
It's more of a matching tool, though. If you keep your records, you'll be straight. Just don't throw anything away in case an audit comes knocking.