The Warbikes (and any Mounted unit for that fact) would gain a -1 to hit modifier (but no cover save) if in base contact with a vehicle (whether friendly or enemy).
It helps to quote the whole sentence from the Mounted rule:
Quote:
Mounted units count as vehicles for terrain effects, and as infantry units for all other purposes.
There is no FAQ needed for this.
Mounted simply makes changes to the way a unit moves. Mounted units cannot enter buildings, jungles, rivers etc as mentioned. They also make Dangerous Terrain tests when entering certain terrain types ( ruins, woods etc). That's really all there is to it. For all other purposes they are considered infantry. Infantry gain a -1 to hit modifier for being in contact with an armoured vehicle. Mounted units gain the same bonus. Being in
cover is not directly related to being in terrain.
I hope I've explained it clearly enough...
Just to help clarify my first comment a bit more:
Quote:
Q:Can an infantry unit claim cover from enemy armored vehicles?
A:Yes. The rule as written does not distinguish between friendly and enemy vehicles for cover benefits. Some groups feel this is an odd situation and house rule that the cover from enemy units is not allowed, so feel free to cover this in the 5-minute warm-up with your opponent.