I don't know for sure, but I think it's probably (b), but at some time I've not pinned down yet. At least, this was my experience - I had a T class to DEL and was checking several times a day for availability to MFU. I was 6hrs behind in Dallas at the time. It wasn't there before midnight UK time (several checks idly during that day). It
was there a few hours later - so I stayed up until midnight Dallas to call the EC at 6am sharp and grab it
I know it's a bore...but it's so worth it if it comes off! If it is (b) though and anyone can help pin down the time, that would be helpful to everyone. I suspect it'll be some weird early morning UK time.