Shouldn't this be an IAG project, or would that make it even worse?

Changing the scope of an IT migration from just BA to all of IAG makes the task significantly harder, but in the long term is the right thing to do - the CEO will likely salivate over all the potential long term "synergies" that can be achieved (job cuts to you and me)
That said, France and Germany are raising the question with the EU about BA being a non-EU carrier and what IAG should do about it - this is a strategic question of much greater urgency to a CEO than IT system re-engineering

I remember reading somewhere that a surprising proportion of worldwide IT expenditure (can't recall the exact %) is spent on migration projects.

A good friend of mine is a senior manager of software developers and support staff. About five years ago, a small company recruited him to migrate them from legacy systems to bring them up to date, After two years of struggling to get them to agree to what was needed - they still clung to the old systems. There was proof that they could save money and do much better on the small things that did migrate. Eventually, he realised they were not going to bite the bullet and left for another company. His pals have had similar experiences.

In the mid-1990s, when I was in telecommunications, I was working a contract for a large and well known UK high street company. The IT Director reported to the CEO which was good as we thought they took us seriously. Then the CIO was told to report to the finance director - who reported to the CEO. Effectively, demoting the whole IT department becuase the CEO thought that IT was all about money. What we did was ensure that every item was tracked from manufacture overseas through to ownership and guarantees.

In my view, most managers just do not understand IT and, therefore they ignore it. Hoping that the problem will errupt on the next man (it's always a man) who takes the hot seat.

Russia flight ban
 

With BA now banned from Russian airspace, how will they route to Beijing, Tokyo etc?

at the moment they don’t fly to Beijing or Seoul. Tokyo route is cancelled and I guess passengers can go on the JAL flight which has a BA codeshare.

It's happened again, app and website down, aircraft stuck on stand, global IT breakdown at BA. The whole operation will now slowly grind to a halt.
Again

Russian cyber attack?

What if it is NOT a coincidence, it could well be a cyber attack this time.

Russia wouldn’t need to bother. It’s an open fact that BA’s IT goes down on at least a weekly basis at the moment.

That’s not a fact though is it? BA have had a few IT issues recently, but the IT going down at least on a weekly basis. Sounds dramatic, but hardly credible as a statement.

check out Flyertalk. There are threads there on it. It went down on Tuesday and at least there were reports the week before of the website not working for a period and the week before that. If you prefer I’ll say it at least has had monthly issues with its IT either website going down, app not working or the Fly system going down.

There are definitely glitches on Avios. If you press search again you get combinations of your previous destination or previous dates.

https://www.bbc.co.uk/news/business-60533275
"It is understood the system issues are not a result of any cyber attack."
All A320-family flights out of LHR between 6am and 11:59am cancelled.. 85 round trip flights all with EU261 liability

That number sounds a bit high - there are usually about 50-55 such departures pre-midday on a Saturday.

When are BAW ever going to get a grip of their antiquated IT systems?

Not just departures, it looks like inbounds are being cancelled too. Nightstoppers, including those at BCN, FCO, ZRH and PRG, all appear to be stranded at those airports.

I dont think Fly ever worked since the got rid of PRS. It was an old system but seemed stable.

I thought Britain had left the EU?

The legislation remains in place until revoked and/or replaced.