The photos don't show any dates but do state that a "few" days ago so the exact date of the photos is unknown unless you can find some evidence of the date on the photos.
Plesetsk Cosmodrome is located some 800 kms north of Moscow on the rail line to Arkhangel'sk.
From my experience on at least 2 or 3 occasions watching those incredible clouds that were chemicals released from the rocket on it's climb all those years ago, the distance to Woomera of 770 kms from Horsham is almost the same as to Plesetsk at 800 kms north of Moscow so to see this phenomena in the right conditions from my experience, is no real problem.
And I would assume that this launch, if it is a rocket malfunction as I have guessed, did take place from Plesetsk Cosmodrome.
Baikonur Cosmodrome some 2000 kms SE of Moscow is beyond any visual range for anything like this.
The only other launch site where a malfunction of this spectacular type that could be seen from Moscow is Kapustin Yar, south of Volvograd [ Stalingrad ] on the Volga river.
However the light at the lower latitudes would not have been suitable to show up the vapour cloud due to the sun position compared to the near continuous daylight up near the Arctic Sea at this time of the year.
My brother and I did a small experiment many years ago and found that in clear nightime conditions, we could see lightning in the tops of thunderheads from 400 kms away so a rocket malfunction on this scale, a few tens of kilometres into the atmosphere would be no real problem to be seen over an 800 km distance on a clear night.
From memory, even the elevation of that enormous vapour cloud is similar to the lowest cloud of chemicals released by the British rocket.
I seriously doubt that this phenomena had anything to do with Arianspace / Soyuz launch
And in fact that whole press release is puzzling as Arianspace is the European satellite launching organisation who in this case have apparently launched a Russian satellite on a Russian rocket from a formerly secret Russian launch facility.
Something does not add up there even though I have read the press release on Satellite Today.
Not directly related; Russian Space Web.com
says that the Soyuz FG rocket lifted off on May 27th for the Space station at 14; 34 ; 53 Moscow time for the ISS which is a half an hour after the supposed time of those photos.
Furthermore, Baikonur is a couple of thousand kilometres SE of Moscow and it would not be possible to see any launches that went wrong from Moscow.
Russian space launches for manned flight are always done from the Baikonur aka Tyuratam Cosmodrome, the major old soviet and Russian Republic civilian launch facilities which since the break up of the Soviet Union is now in Kazakh Republic.
The advantage of Baikonur is that as it is closer to the equator the speed of the Earth's rotation towards the east, the launch direction across the steppes, is added to the rockets velocity and allows much heavier payloads to reach an orbital velocity for the same fuel load.
Plesetsk being up near the Arctic circle doesn't have this advantage and is used primarily by the military for research and satellite launches particularly polar orbiting satellites which can cover the entire globe every 24 hours as the earth rotates under the satellite orbit.
The Russians were considering abandoning Baikonur as it was no longer on Russian soil and were proposing to build new civilian launch facilities at Svododnyy in the Russian far east.
However I think that the Russians and the Kazakhs came to an agreement a few years ago which enabled the Russians to use and control Baikonur for a long time into the future.
All in all I will stick to the theory that a liquid fuelled military launch vechile, possibly in tests or even in a practice launch with a now obsolete liquid fuelled launch vechile was launched possibly from Plesetsk, went AWOL and the controllers lost control.
The launch vechile started to break up and released it's fuel load high into the stratosphere or even higher and the rocket then ran out of fuel and from the appearance of the very RH end of the vapour cloud appears to have blown up.
I am no expert at all on the rockets nowadays and have only used what I can find on the net plus some background knowledge and the rest is deduction so I could be very wrong.
If so then I will be most interested in any alternative explanations that have a good grounding in fact.