So, obviously I'm not engineering, but here's some things I've discovered in my science degree:
-In first year, you'll meet a few people, might see them again, but you really start to realise pretty much what Aaron suggested - you'll need to put effort into any friendships you want to keep.
-In second year, you'll start to specialize in the stream of engineering you want to do. Now, as it turns out, a lot of people at this point will be on VERY similar trajectories to you. You won't share all the same classes, but at this point, you'll probably find a few people in the same stream as you who are doing the same units.
-In third year, you'll basically hit pinnacle high school social life. Everyone will be doing the same units as you, with small variations. You'll probably have a clique of people all doing the same stream of eng, all doing the same activities. At this point, they're more like a bad smell.
-In fourth year... No clue, soz. This is where science and engineering are really different. /shrug
But yeah, essentially, you will be in a position where you know a bunch of people in your "cohort". It's still at least a hundred-something person cohort (up to 500 I feel? Just based on the many different streams, cutting that up from a few thousand), but it's not going to feel like a high school social setting again until third year. However, you might find some kindred spirits in one of the MANY engineering clubs on campus (in o-week, check them out - apart from the main society, MESS, there's a club for each stream. Or close enough, at least). Otherwise, look for friends in special interest clubs, like the board games club, or the harry potter club, or circus club.
Don't stress too much - if you can put in the effort to go to events and talk to people, you'll make new friends. If you can't, well, you're going to have a bit of a rough time.