Earlier this week, the Chicago Sun-Times (my old bailiwick) reports, O'Hare Airport opened a new indoor rest room in Terminal 3 for service dogs. (There are also three grassy spots outside where Trooper can transact his business.)
Props to the airport. Every human member of a traveling service dog team always worries about where his buddy is gonna go. Especially when the team has just gone through security.
Practically speaking, however, Trooper and I do most of our long-distance traveling by train, and we depart from Union Station in Chicago. That facility doesn't have a canine rest room, but neither does it have Homeland Security gates. There are no grassy areas nearby where dogs can relieve themselves and not get yelled at by building rent-a-cops, so service dog teams have to be creative with light posts and the few available flower beds.
Amtrak is presently refurbishing Union Station from top to bottom, but I doubt very much that it'll provide any special space for service dogs. There just aren't enough of them on the rails to bother with. It's a nice dream, though.
Things are a little easier once the trains have departed from Chicago. At stations where there's baggage service, the trains stop long enough for passengers who smoke to take a few puffs—and service dogs to take a break. Usually grassy areas run right alongside the platforms, and train crew can often direct dog teams to the most convenient spots.
It's never a piddling matter. Just ask any service dog team.