|The following is based on Van Buren and has not been confirmed by canon sources.|
In or before 2250 he traveled from Hoover Dam with Agnes, Goddard and a large group to the Dome in the same truck. It was meant to be a drivable vehicle, and could be acquired by the player (although over Eddie's dead body).
Once trade is established with Denver, Galenski and his truck will be off the map for about a week once a month. The player can try to take his truck, but he won't let you take it (you'd have to kill him), and it's not made for off-road travel (it's tires and suspension will go out, making it a landmark/base but no longer a vehicle), so you can only take it from Boulder to Denver.