Unspecified in RAW -> DM call.
Here's a conundrum for you, though:
If on gaining a template you don't get the XP, what happens if you thereafter lose a level (due to a failed fort save vs. a negative level, or from Reincarnate/Raise Dead/Ressurection)? RAW, you're set to halfway up from the level it put you at... so if you're 7th level Fighter and become an afflicted Lycanthrope by way of a werebear (CR 5), you gain 6 racial HD and a +2 level adjustment (ECL 15 with your levels in Fighter). If you later are Raised from the dead via Raise Dead, you lose a level (to ECL 14), and... are set to halfway between ECL 14 and 15 on your experience regardless of your previous XP total.
Nifty, huh?