Networked ITV - 1990s and before...

Nope, by the looks of things it's been taken down for good, unsurprisingly as ITV are moving out of Quay Street in the next 2 years

Tvvats

It was a completely clean feed, Border retained their own transmission, with a technician in Manchester rolling the commercials to cue from the duty TC.

The post 1993 partnership wasn't a take over - its was a joint sales agreement. The two regions were sold as one 90% of the time, part of getting a higher rate for the ads, was that they were shown on both regions within a few seconds of each other, creating a macro region.

It was purely a commercial decision, with no real thought given for viewers - many continuing series jumped loads of episodes overnight - for example I think Prisoner Cell Block H jumped 90 episode overnight. It also enabled Border to get rid of a lot of its day to day operational stuff, like most of its VT department.

I thought the sign was listed, in a similar way to the TV-am sign outside their former studios in Hawley Crescent, London.

It is/was - but they could take it down as apparently it was corroding and thus liable to drop off at any moment (if you believe ITV...).

Did Border play out their own trailers etc or was this also taken over by Granada?

Im surprised TT and border never got together instead, I dare say it would not have been so bad, for each other.

Most ITV companies were cooperative with each other most of the time, even in the days when they were totally separate entities. For instance, when Mr and Mrs was commissioned as a network show, Border's studios were black-and-white only, with local programming, apart from films and other series made on film, monochrome until mid 1973. So the first networked series was made in Newcastle as a Tyne-Tees/ Border Colour Co-Production. Again, both Border and Grampian helped STV out when there was a major studio fire back in 1969.
ISTR, the first bid to merge with Border was made by STV. It would have been interesting to see how things would have worked out, had that arrangement gone ahead. Border's fate was sealed when they became part of the Granada group. Having said that, STV has not done much to preserve Grampian's heritage, although there's still a local news presence.
A Tyne-Tees/Border merger might have worked better in the short term, but it was clearly the goal amongst the "big beasts" in ITV to have a single service for England, apart from the token news service that currently exists. And, of course, a quarter of a million Scottish viewers are currently in England for their channel 3 service.

None of the stations will have got together to any great extent before 1993 (just the odd loose arrangements for some common imported programming etc). After 1993, we'll never know because of history.

If TTTV hadn't had to fight off Granada, they would have possibly been another £2000 uncontested region. Then some kind of merger between TTTV and Border might well have been in both companies' interests to fend off larger stations in the early years (TTTV and Border being one of the very few examples of two small stations next to each other but not overlapping to any great extent, and two low bidders would be cash-rich, so it could have been a marriage of convenience with few cutbacks required). It may well have ended up happening.

I dare say STV would have tried to take over or Merge with TT/border. it could have created a small power block to the north of the main ITV.

STV has done well with Grampian under the current terms, it still has its own local news AND two separate opt out within the news. Ident seems to be mix between old Grampian flag and STV Name. Local programmes are thin on the ground all over the uk but it has to be better to have control in main office only hour drive away instead of on the other side of the UK.

STV tried it best to keep a finger in local station.

A don't know why Ofcom don't get a grip about the legacy Border area. The IOM was sensibly reallocated to Granadaland. Post DSO Caldbeck carries two completely separate PSB 2 (aka D3/4, aka ITV/C4) muxes.
One for Scotland, (that also feeds all of the Scottish Caldbeck relays for PSB 2) and one for Cumbria.
Selkirk has virtually no English viewers, and the only English relay (Berwick) was allocated to Chatton (a TTTV Tx) back in 2008.

So, Ofcom could easily allocate the 'Scottish Tx network' to STV. The loss of ad revenue will be very small for ITV Ltd, it's tiny compared with all of England and Wales, and the loss of Scottish news reports on TTTV would most likely increase TTTV's viewing figures in their heartland.

On the flipside, I'm actually quite surprised that ITV didn't take advantage of the position they found themselves in, and changed the split. A "South Scotland" regional programme would be extremely popular with viewers I'm sure even if it is broadcast from England, and Cumbria viewers are well-used to a NE&C regional programme.