The uniform part makes sense, but a working vehicle of that sort and power just sitting off by itself I'm not so sure about. The military would've taken it as their own already unless you have a good reason as to how it got there and why it was abandoned. I had another plan as to how they would escape, but it's a bit different. If you want the group to come across that vehicle then they can, but maybe not quite just yet. Obtaining a vehicle like that without trouble just seems too easy.. I dunno.