Yes, as long as you can get the emitter deep enough into the reflector at the focal point.
If it was a Luxeon / Seoul reflector, you might have to raised the XP-G into the reflector, as the Lux and SSC package raises the die quite a bit.
If it is an XR-E reflector, i have read recently that the focal point for an XP-G is 3mm aft from the XR-E focal point. This is because of the dome/optic on the XR-E shifting the apparent image of the die. The XP-G has much less shift due to the dome.
Personally, i have managed to get the Streamlight Survivor LED reflector (designed for Lux/K2, to work with a SSC, XR-E, as well as the XP-G. All had beautiful beams - it is a great reflector.
The XP-G has identical beam to Lux/SSC, but with a slightly larger hotspot due larger die.
Hope this helps!
