Getting vehicles to spawn with invasion mutator?

[»TheHitMan«]

I am using this invasion mutator with my vehicle DM map here to better combat the monsters:

http://forums.epicgames.com/showthread.php?t=590438

However the vehicles don't spawn at all, how can I get my vehicles to spawn while using the mutator?

[udk3]

I remember using that invasion before, vehicles were there on maps with them. Have you tried rbtt invasion? They have the source scripts too.