At UTS the social life really is what you make of it. There are plenty of places to hang out and meet people but you've got to go out there and make an effort to talk to them. If you're on the shyer side and are less confident about approaching random strangers, the clubs / societies are a good way to meet people. Since a lot of your friends are gonna be on different timetables to you, joining a society that has regularly scheduled activities is a good way to form and maintain a consistent friend group.
And BlueGas is right. The buildings aren't 'scattered across the city' at all. Most of them are centred around the alumni green and/or nearby it. The only ones that are far off are the business/law buildings which consists of the new one (mostly for post-grads) and building 5 which is subdivided into several sections that surround a couple small courtyards.
If you plan to spend a lot of time on campus, UTS has a lot of indoor places to chill with friends too, which can be a bit of a relief when it's cold and rainy. The downside to its city-centre position, however, is that there isn't much grass. No big sprawling grassy areas. Just the smallish strip of the alumni green that on nice days has beach chairs and stuff put out on it. Also, unless you're in business or law, since all the buildings are close together there's no big hike between buildings to get from lecture to class.