If they ignored warnings from even relatively friendly states then I find it difficult to see the whole thing as something other than sacrificing some of their own people so they could wring some propaganda out of the event to shore up support for their war. When it first happened and they tried to lay the blame on Ukraine I figured it was more a case of, "Never let a serious crisis go to waste," but it really seems like they knew it was coming and allowed it to happen.
So everyone and their mother warned them beforehand, but they allegedly knew nothing. This has some 1999 Russian Apartment Bombings vibes. Not that it is any surprise anymore at this point, that Russia would sacrifice their own civilian population to push an agenda.