The "former" shareholder cannot vote the shares if the share certificate held by the former lessee is cancelled on the books of the corporation.
The corporate by laws set the rules on voting, and so, this is not subject to an answer on AVVO.
The usual provision is that the owner of record of the share certificate may vote. If the corporation cancels the existing share certificate in favor of a new owner than the old share is no longer on the books. If the corporation issued a new share certificate and a new lease (the lease is the agreement that allows an owner of shares to occupy the apartment etc.) then the owner of the new share certificate votes.
Please have an attorney for the apartment corporation get involved with this matter.
The answer provided to you is in the nature of general information. The general proposition being that you should try to avoid a bad outcome if you can.