As paults said, the Roland Strat has a GK-3 PUP, which is magnetic. It's no more susceptible to feedback than any other strat. After a couple of weeks with this guitar, I still like it, though I tend to play the regular strat PUPs more than the emulations...
I understand these are regular pickups in the guitar.
Do you know if these pickups are designed just for this model and can they be bought separately to be fitted in other guitars?
u can go either route on numerous makes of guitar, RolandGK pickups are best for stability and working as expected(loud places etc 
), Piezo are best if you want a 3 voice guitar for blending to bring acoustics to life etc... I don't know which the VG Strat uses as I stick with VG99 for its editing potential. I would try all the possibilities available to you and decide what works for you, as journey to the digital side is expensive. good luck with it!
I understand these are regular pickups in the guitar.
Do you know if these pickups are designed just for this model and can they be bought separately to be fitted in other guitars?
GK-3 pickups are available for purchase by themselves, but they won't get you the rest of the electronics that are in the Roland guitar. You would need a VG99 or a GR55 to get any functionality out of them.
