I've measured with an external, unconnected RF monitor. The cell phone shows clear activity when not in airplane mode, and then zero activity when in airplane mode.

There's my anecdata...

I was told: "I suspect that in airplane mode it would only communicate at the specific request of the system (and perhaps in spread spectrum mode), so [before baseband is activated from outside] it would not be worth measuring." What do you think?

Isn't that... totally expected? After all, it's the system that told the modem/baseband to enter airplane mode in the first place. Of course it can also tell it to exit airplane mode.

You are right, bad translation. She was trying to explain that the problem is that, independently of you and against your will, the remote telecommunications system is able to activate the broadband chip of your mobile phone while it is in airplane mode, where you expect the baseband system to be deactivated.