Yes. Backwards compatibility to Dolby A was thought of as Dolby A was also a pro medium , unlike Dolby B and C. I personally have never tried to do this, but it does suggest this is the case from literature i have read on this.
More over i would check the bias of the tapes you have and sort of tapes they are, and check the compatibility to the new machine, the place you hire from 'should' know this sort of info....if they have not asked you, i would be dubious, and go and find the info yourself. Hoper this is somewhat helpful.