There are lots and lots of SPs that advertise they are "certified" as massage therapists. In fact, many SPs who work in massage parlours are "certified" in some sense or other.
But - do not confuse someone who is "certified" with someone who is an "RMT". They involve two completely different kinds of training, education and certification.
If you find an SP who is "certified" and if the question of certification is really important to you, then you may want to ask who "certified" her.
Since you're not likely to find an RMT who provides "extras" with a massage, don't get overly hung up with the question of "certification". Instead, search PERB for SPs who are reputed to give a good massage and then try them out for yourself.
Some ladies who have been reviewed on PERB as giving a good massage also have or claim to have some form of certification, such as Chelsea (aka majictouch), Madeleine, Joanna and Leiah (sp? - in False Creek). Frankly, if you're looking for a therapeutic massage go to an RMT and book a full hour session rather than the lame 20 minute sessions you get with the medical plans. Cost is about $70 to $80 per hour. Now that the therapeutic part is taken care of, go see a great looking SP who gives a great erotic massage and HJ and enjoy it for what it is.