So many agencies involved now,I get the feeling they have rough idea where the T7 is.
But if you trying to catch a car thief you won't broadcast to world you know where they are and coming for them.
Hence the Southern corridor.
I had thought this too. I can imagine a scenario where they've located it on the northern route, on the ground somewhere - but have not announced it because they are figuring out what action to take next, whether passengers are being held, etc.
Wild speculation, but as possible as anything else.