-- place a Trigger in the middle of your Lift Mover
-- Trigger Event = Mover Tag
-- TriggerType = TT_ClassProximity
-- Trigger ClassProximityType = Onslaught.ONSVehicle (or whatever vehicle type you need for your map)
-- set Mover DelayTime to 0.5 to 1.0 sec (gives the vehicle time to get fully on the lift)
this should get you started, at least. i tested it with an Onslaught tank and it works, subject to the caveats below.
NOTES: vehicles and Movers interact oddly. unless the vehicle is occupied and has some velocity (even really small), the vehicle will not interact with the Mover, perhaps due to some aspect of the Karma coding. so vehicle lifts will be unreliable at best unless some workaround is developed.
a similar problem affects XMP vehicles. i wrote a small scripted actor for XMP maps that wakes up the karma of unoccupied vehicles when a mover is activated -- something similar might work for UT2K4 vehicles as well. if you're inclined to scripting, look in the classes for the KWake() function, see if & how it's used. if it's in there, you might be able to use it as i did in the XMP fix. be sure to test it thoroughly for netplay!
also note that unlike XMP, in UT2K4 you apparently can't base a VehicleFactory on a Mover, so vehicle spawn points will have to be placed elsewhere than a Mover/lift.