IGN reports that the RB Strats don't work with GH.
Honestly...I don't really care all that much. I hate Stratocasters, especially fisher-price versions of them. But hey, it's Rock Band! It's a different game really. We are quite lucky that the Explorer guitars will be forwards-compatible.
I'm sure the people that wanted Guitar Hero already have it, so I'm doubting this will be a big deal. Was anyone out there holding out so they could avoid having to purchase a GH guitar?
(btw, nice image-find the 'stiq)