Yes Mike's right, I've used XP2 at 1600 and 3200 EI however that's with push processing in C41 chemistry.
When Ilford released XP1 (there was no XP John) it had a non standard C41 process time which labs didn't like, there were also push process recommendations in the Ilford data-sheet.
XP2 was an improved emulsion using the standard C41 development time to make it easier for consumer C41 labs. Ilford dropped the push processing times because labs didn't want to do this.
I adjusted my push process times to suit XP2. Around that time I was having business meetings with Ilford at Mobberley and remember talking to two of their directors and a research chemist about push processing XP2 over lunch. They told me the only reason they'd dropped any mention of push processing was because the labs didn't want to do it.
XP2 always gave me far better results push process than HP5 or even Delta 3200 when it was released.
This shot of Vana was XP2 push processed, (hand coloured).
Ian