I agree wholeheartedly. Any organization, in any sport, that wants to maintain any amount of respectability amongst its peers (which most, if not all, do), will almost always let employees interview for any position that could or would be considered a promotion. Especially if they appear to show an aptitude for it, which looks like the case here.
While I admittedly don't know much at all about the Boston organization, I have to believe that they operate under the same principle. Even if they'd hate to lose him, they're unlikely to stand in the way of a promotion opportunity that they're not in a current position to offer.