Create a west solider of a high rank and set him as the leader of one of the groups. THen put in his init field: deletevehicle this.
Then crate a east soldier of a high rank too, and set him as the leather of the other group. Put the same in his init field.
Also you could hack the .sqm file, but since I've never managed to make that work, I think that what I've told you will work fine.