I've only had my boat for a year and a bit on the Bridgewater but my parents boat has been on it since '99.
I've only ever seen workboats tied up, no maintenance at all has been carried out as far as I'm aware.
There's a boat called Water Womble who you can see out and about now and again when the weather's nice... the guy has a nice big fishing net and scoops all of the ugly bits of floating rubbish off the top of the cut.. as he's floating (JUST!) over the shopping trolleys, road cones, fridges, beds.. the lot.
I appreciate that every canal has rubbish in it but I have never seen any sort of maintenance, or dredging being carried out on the Bridgewater.
After they had completed the new 'Stretford Marina' I tried to take my boat down the cut to have a look. I had rope, a coat and some bags on the prop on the way back and a length of wood which was about 6 inches thick/6 foot long(ish) wedged passed the skeg, beside the rudder, through the prop and wedged up the weedhatch. It's a good job it's only a 30ft boat.. I was able to stop it in time before I wiped out a cruiser moored up minding its own business...
Took me several attempts and a helluva lot of patience to eventually get it off but luckily no damage to the boat.
So much to say and not enough web space to say it all