I don't own a G2 or G2 Pachy forend to try mounting a Contender frame just to see if it will even mount/function correctly... but no, they are not the same. Not the same part number, not the same shape and not the same price. Because of that my guess is they are not interchangeable.
Somebody here will have both though, can try a G2 forend on a Contender frame and can confirm it will work and function correctly. If the G2 forend will not work on a Contender frame drop me a PM as I have extra Contender Pachy's.