A bit like leeches
"By our reckoning, they would pay a couple of percent for this in the form of revenue-sharing..."
The Post Office could charge extra fees for parcel delivery based on the profits of the company sending parcels to customers.
"This would be a fair contribution for the use of the infrastructure."
No, a fair contribution would be to pay the standard rate, whatever that is, the same as all the other customers of the telco.
Wasn't it the boss of another German telco, some years ago who said (paraphrasing), "I see all the money that Google makes from its internet services and I think it's only fair that we get a percentage of that".