When applying, for now at least, you still apply for either Sig Op, LCIS Tech or Lineman specifically. I had asked my recruiter about a few things regarding Sig Op, then corrected myself with ACISS, and she asked me where all this ACISS stuff was coming from. She had heard nothing other than little bits from applicants about it, and as far as her part goes, still continues on like normal with recruiting for each trade.
I don't see it changing on the entry level for a long time in my personal opinion. Would make it a little difficult if down the line they have a huge shortage of Lineman-Specialized ACISS's, so open 120 spots for ACISS, only to get 120 applicants who only want LCIS Tech, and decide/request to specialize in that when the time comes.
To the OP, I originally wanted Infantry, just like every other 17-year old wannabe ninja sniper out there. 'Wanted' it so much that I didn't even bother looking at anything else. Once I had actually talked to a recruiter, who opened my mind enough to realize there is actually a lot more to the CF than Riflemen, Pilots and Guys-That-Look-Through-Periscopes, I was quite surprised to find quite a few trades that I would be quite happy in for my career within the CF.
I know it gets said here a lot, but really take the time to go through each of the trades on the forces.ca website. Don't limit yourself to simply in-demand trades because you want to be wearing boots 'Right now!', browse through ALL of them. The various subforums here also have a lot of specific information about different trades, you just have to be willing to look.
My :2c: