Using content packs with RTS engine

Just a quick question, I know its probably something really easy but I still am having trouble getting my head around this stuff. Is it possible to use the content packs with the RTS engine? What is the scale of stuff? Are the units the same size as the fps units and the buildings the same size as the fps buildings so you can just drop in content pack stuff. Or is it a totally different scale? If so, is it easy to scale the stuff down to fit?

Thanks in advance,

-Will