When a Officer completes the Special Forces Course, they would retain their rank(they did in the past, and I assume they still do) and MOSID. If a Officer wanted too, I'm sure they could submit a memo, etc asking to relinquish their commission and VOT to the CSOR Operator(NCM) MOSID.
Gerard8, if you are serving CF member you can always email/call the CSOR Recruiting cell. If you are not a CF member, I wouldn't worry about CANSOFCOM, but instead focus on getting yourself ready for the military, then once in focus on the course you are on, then the next, etc. Two years in the CF is required before a member can apply to a CANSOF unit.