It's already here, or was here. I saw it last week - but I'm racking my brains as to where. I think I was on an eastbound GLQ-EDB shuttle and I saw it going west, but I don't know if it went as far as Queen Street. That would have been on Monday early afternoon.
It comes up to Scotland for testing every couple of weeks, it was in Glasgow a few days ago, it also does the Edinburgh to Glasgow as well, it has also appeared on the Airdre to Bathgate line before for testing