Unless you're going there do to a medical degree, then yes, Id see no reason why not.
The only reason I say that is that MASUAS currently has 3 medics on bursary/cadetship/whatever the name is on it's strength who are at Queen's. I know this because I too am a member of that fine UAS.
However, any other degree, it would probably be best to go OTC. We had a boarding officer from OASC down to the sqn a couple of weeks ago to assist with interviews for our freshers, she explained that sometimes they suggest to people to join the OTC rather than the UAS. This would suggest either are perfectly valid.
And if you explain at your OASC board the reasoning why you went OTC rather than UAS, im sure nobody would complain. To view it as a 'lack of commitment' would be really unfair, if there is no UAS available to you, it's unrealistic to expect you to have joined it.
Im sure others will have far better things to say than I do though.