That was just unlucky timing on Granada's part - I'm sure that phone box prop would've been ordered when the old logo was still in use!
And mentioning that, at the start of today's first ITV3 episode we saw they'd changed the windows in the phone box to ones with the new logo! So the phone box would have been on the street for a matter of weeks before they changed the windows- which I doubt BT would have been so eager to do in real life!
IIRC, BT did a pretty quick and comprehensive job back then of rolling out their ‘piper’ logo on phone boxes. I’m still amazed they’ve updated so few with the 2003 ‘connected world’ logo. I know hardly anyone uses phone boxes these days, but to have a logo that was abandoned 16 years ago still prominently displayed in so many places across the country is pretty poor IMO.