Just finished Leon A/Claire B. Needless to say these two things happening at the same time make no sense. So what do you think really happened?
For example, say Leon A is canon. What was Claire actually doing at the time?
-First of all, the underground entrance would already be open for her.
-She'd meet Sherry downstairs, but not fight William and would never fight William until rotating the train car.
-Let's say that the parking garage gate went back down on a timer or something, so she'd still run into Irons.
-She'd be able to access the parking pass without solving a puzzle (since Leon already took the items from the clock tower) - the office cage would just be open.
-She'd get Irons' call and go to the orphanage as shown in the game
-Sherry getting stuck in the garbage room wouldn't happen. Claire would meet up with Annette for a very short time (perhaps while she already has Ada trapped) and agree to take Sherry to the lab to find a cure for her illness.
-Annette would just give Claire the wristband to go directly to the cure and it would be uneventful. She would return and cure Sherry.
-Claire's fights with William at the end of the game happen as shown.
-Sherry and Claire would not know what became of Annette (Leon would have to tell them on the train in an scene not shown, so this is one bit that doesn't fit in too well)
If Claire A is canon:
-Leon goes immediately underground
-Leon meets Ada but doesn't fight William.
-Ada is not captured by Annette, she simply comes and goes as she wants.
-Ada gives Leon a wristband that will get him all the way to the G-virus, treating him as a pawn.
-Leon gets the G-virus with little effort, triggering the self destruct. Leon does not find out who Ada really is, but is suspicious when she asks for the virus (I guess there could be some situation where Leon runs into Annette and they have a similar conversation to what is in the game)
-Ada "dies" in the same way when the bridge collapses.
-Leon fights the Tyrant as shown in the game.
It's a bit silly, but a fun thought experiment. I was just a little bummed about how badly the A/B stories connect and wanted to come up with some headcanon.