Localised jamming of a passive system is surely going to simply highlight the presence of the aircraft you are trying to hide.
To make it work you would have to take out the countries entire potential passive networks. You'd need something on the scale of the old Russian "Woodpecker" OTH radar - remember how that used to completely blat out short wave radio, but the harmonics would also be picked up by the phone system - blocking calls. I can even remember it blocking TV signals. That was 10MW or thereabouts. How much power would you need to flatten a countries mobile phone networks? Could that be broadcast continuously from an aircraft? And how do you localise it so the neighbours don't complain? But whats the danger that the signal itself can be used as a radio source for passive tracking of the aircraft you are trying to hide....???
A lot of imponderables that no-one who knows is going to answer. But I stand by my view that the delay in production will render the aircrafts technology totally irrelevant
PS and before anyone starts shouting that third world countries don't have mobile phone networks - many of them do. In many cases a mobile network is a cheaper capital project to build than a cabled system.
For instance, I suspect this map of the coverage of just one of Iran's six or so mobile phone networks covers most likely targets
Mobile World Live - Coverage Maps