I can very seldom get the app to connect to the car when it's parked outside the house - there is generally good reception here. However it did connect fine yesterday at my dad's place in the country where reception's usually pretty bad.
However the other day I must have not closed the boot properly and when I opened it, the car alarm went off. I then got a barrage of text messages from MG about the 'unauthorised entry'. So it must have a cell connection in order to send that alert to MG.
All in all quite puzzling.