i dunno what the deal is, but i think the last resort ends up being claiming unreimbursed travel expenses for work on taxes at like 60 cents a mile or whatever the federal rate is.
which is generally a shit arrangement, mostly.
one would expect there to be a rule about expecting employees to cover transit to infrequent/uncommon remote locations out of pocket, but even among the chiseling orgs i worked for they didn't balk at throwing me the $20-30 bucks for some rando trip out if town they wanted me to go on.