If you read that website you will see PSAC does not represent foreign service workers. So while PSAC may have something to do with CIC (as they are in Canada), they would have very little or nothing to do with CEM (which is not in Canada).
I would assume that PSAC workers handle stage 1 processing. And as we know, that has not been affected by the strike. It is the embassies that are affected.
Also, while some PSAC members are sent on foreign assignments from time to time, this
http://www.psac-afpc.com/news/2013/bargaining/20130730-e.shtml makes it very clear they won't be taking over for PAFSO workers.