I have the same problem. I can place trucks, ships, MTLBs, BTR-80s, and T-72Bs in the mission editor, but only trucks are actually in the mission when I play it.
In fact, they're even missing from the A-10A Caucasus Close Air Support mission as well. No enemy units except for the Hinds, lol.
I just did a full 'scan every file' repair and it didn't help.