Not quite how it works. Once you get to HQ and Sig Sqn, you'll most likely get tasked one of the troops. One does mostly TacRad, RRBs, outdets, etc. The other generally set's up, supports, and mans a Bde CP, and the other is IS and tech support. Couple of different jobs as well, but right off your 3's, you'll probably go to TacRad or CP.
End of Jan, early Feb'll be a good time to get here.