Well I figured this question would be answered within a day - but since no one bit - I'll go:
Ok first off, I'd like to cover my butt by saying I'm not a Private in the Bde so I'm not the perfect person to give out the best info. Secondly, I'd like to add that NO MATTER WHAT any one person tells you it's going to be like for your friend, I can almost guarentee that it really won't be. Not sure why people like to exagerate/elaborate so much. All part of story tellin I s'pose.
So I THINK that as a new Pte (Sig) in HQ & Sigs, you would be basically an entry level Signaller. You could expect to possibly be a driver (Iltis, LS maybe - depends on the quals and the need). You could end up being a det member but if you just came off of your basic trades training, then you should expect a Tac Rad det as you are now considered to be ready to go in that department - under a normal level of supervision and guidance of course. I believe that as things seem to be changing very fast now in the trade, you could expect to find yourself (your friend) doing quite a bit of training. Could be mostly exercises, troop and squadron level run stuff, but maybe you'll find yourself on some more formal training depending again on requirements.
As for day to day - that's really a question to be answered by Sig Bloggins that's there right now. I know when I was there it was det maintenance, sweeping, shovelling, refresher training, anything really to keep out of the watchful eye.
I think that a basic Private in any trade will most likely be in the same boat. Janitor, coffee maker, runner, getting your feet wet before you're thrown into the pool so to speak.
Anyway, to anyone who wants to poke holes in my info, I bow down to the superior recent experiences others may have at this type of unit. But again, I think it could change at any time. Oh, it just changed right there. Did you feel that?
I'm not sure if Sigs are going directly to the out units right now either. I know it does happen sometimes, but with all the training that they need first, it's sometimes best they spend a few years in the Sqn before moving onto a Sigs Pl where there is less of a watchful eye. But yes, it is possible to get posted to almost any other unit on the base. Again, you'd usually need those basic "vehicle skills" and a good level of knowledge of the trade. Which you would have by the time you're looking at a posting anyway......hopefully. In my opinion, I think being at the outunit is where it's at. You really get to shine your stuff and do your job without having over a hundred other people (literally) criticizing what you do. But alas, "THE SQUADRON BUNGEE CORD WILL ALWAYS PULL YOU BACK". That's where training begins, and should be where the specialists are taught. And I'll tell ya, some are special all right.
Good luck.........to your friend.
Bin