This is not an 'intranet' it's a metropolitan scale network with tens of thousands of users personal machines connected to it.

Of course they use DPI for a variety of things however it does not help for this specific instance as because they are *personal* machines you can't MITM the https by installing trojan certificates on the client machines.
Which morally you shouldn't be doing anyway even if you are running a locked down corporate network.

Also the stuff required for doing DPI at line speed on 20Gbit/s links is expensive.

A real one?

This is MITMing https via a Nokia wildcarded certificate installed on the phone.

Amazon Silk on Kindles does the same and shouldn't be touched with a barge pole.

Opera MINI does the same but is worse as you end up with a secure connection from Opera to the site in question and an insecure connection from you to opera. Again should not be touched with a barge pole.

True smartphone browser such as Safari on the iPhone and the built in android browser provide end to end encryption from the device to the website.

What?

They purchased air to ground spectrum and tried to re-purpose it as ground to ground spectrum. They sued when the FCC told them to go take a running jump.

Then tried to claim that GPS vendors were at fault for not having perfect notch filters in their equipment (hint such a thing is not physically possible)