The link to the RCMP commissioner is that the agreement that the Speakers are going to enter into asking the force to provide that service will be with the RCMP. This director will be accountable in the sense that he will have to make sure the agreement is properly implemented as it was intended to be by the parties.
If you want, I can use the analogy of how the RCMP provides services to the provinces. They enter into an agreement with a province and although the RCMP commissioner is the one entering into the agreement, there is a contractual relationship in which the RCMP serves under this agreement.