A vehicle similar like the Imperial Troop Transport indeed appeared in Echo Base.
The vehicle also appears on the cardboard of the Rebel Commander Center (sorry no other pic available in my archive, it is just right from Leia's head).
Apparently this vehicle is called the Rebel Troop Carrier. Steve Swanseet wrote a nice article about it.
In detail the Rebel Troop Carrier looks a bit different compared to the Imperial Troop Transport. Source: http://starwarsblog.starwars.com/2014/02/03/the-rebel-troop-carrier-from-echo-base-to-rancho-obi-wan/
Still.... it is nice to think that Lucas Film paid homage to the first released Extended Universe Kenner toy by giving a modified version some screentime in the Empire Strikes Back.