I did a neck reset on an Ovation Applause 12-string last year, and it was a standard glued dovetail, necessitating a steam-off and heel cut (ie: the usual procedure). Don't really know if the "Celebrity" is constructed any differently.
I shared the topic with a friend of mine who has worked on some Ovations, and he cautions that he's run-into them with neck joints that have been factory-epoxied. He wasn't sure of the model(s) and couldn't speak to 12-strings.
If that's the case, it sounds like a neck joint to avoid. Good luck.