If you haven't watched "Midnite Spares", then go find it, it's a classic, underrated Australian car movie with actors like Bruce Spence, David Argue and Max Cullen stealing the show from the main actors!
Now, if you're at all interested; The T&T Towing workshop was set in Macdonald St, Erskineville in Sydney's Inner West.
The establishing shots from the film, facing west, show the rail overpass that divides the street. The T&T workshop is supposedly just on the other side of the bridge, to the right.


These are screencaps from shooting circa 1981/82.
Today (taken on the 26/08/2014 (or 08/26/2014 for the Yanks)) goes to show how much life has changed in old Erko'.

No longer a grotty little half light-industrial suburb on the edge of the CBD, it's overfilled with people who own more than one car and can jam a family into a single story terrace house which will now sell for well over a million on a bad day.
On the right is a massive apartment complex in the process of being build and on the left, amongst the dwindling warehouses and factories are more apartments. Every street in the area is wall-to-wall cars because the council think that more apartments and overcrowding is a good thing because they can make a load of money off of strata costs! (Raw nerve much?)

Here we see 'Wimpy' (Bruce Spence) returning from the corner store (Cr Flora St & Macdonald St), back when suburbs had corner stores.

Today: TREES! There are trees everywhere these days, anyone noticed that? That's why older movies looked so bleak, there were no bloody trees!
There are also signs everywhere too, because with that many cars everywhere, you need to decide on traffic flow. Some of these streets barely fit two cars side by side and I guarantee one side is stacked with awkwardly parked 4WD's that have never left the city limits!
But what of the T&T workshop? Well, here's a secret. It's not there.

This is where the created the illusion of a workshop, at no point did they show any closer to the overpass than the previous two screenshots! I haven't got the screenshots (yet) but I suspect that the 'outside' shots are filmed around Jubilee Park in Glebe, where there are a number of work spaces underneath a rail viaduct. These spaces were kinda small, so I suspect further that the inside shots of the T&T workshop was again elsewhere, probably a sound-stage so they could emulate the disturbances of passing trains...
Glad I finally made this post, if anyone else is interest and can corroborate more, we could get some more locations worked out and some more then/now shots!
Cheers!