Mandatory heating rental in new buildings - is that possible?

You forget the economies of scale that occur in such a project. There is a big difference between building 50 houses with individual systems independently and at different times or one system for 50 houses.

And of course he pays for the underfloor heating himself, the entire heating network naturally only applies up to the transfer point. Sometimes I really wonder why you always have to desperately pick fights with everyone and argue with half-baked arguments on the opposing side?

How are the 8 cents/kWh calculated? Electricity? Actual heat?

Working price heat cents / kWh gross.

The OP wrote surface collector, not drilling. That should be significantly cheaper... although I didn't understand whether it is installed on the owner's own property or somewhere else. If it is not a ring trench collector, I wouldn't want it on my property anyway, because then you can't plant trees on the area.

It is designed as a large area along the edges of the entire residential quarter.

The point is simple, compared to now I would pay more than twice as much per year for heating over the next 15 years than I pay now and I don’t even own any of the technology. What happens after that is also only partly clear. This is simply anything but sustainable.
My expectation would be, the more scale effects there are and the longer the packages are bundled, the cheaper it should become compared to other concepts from the last 5 years.
(I myself currently live in a house with KfW55 standard air-water heat pump 140sqm and heating and hot water costs me less than €1000 per year (exactly €891).
That would be fixed in the new building for 15 years, a base fee of €2500/year plus the heating energy price of 8c/kWh, which is not fixed. Honestly, that’s almost a rip-off.
Consider, I also (would) have paid the €25k connection costs just to be allowed to participate in this game. And I don’t own any of it. Zero. Nada.
come on... anyone who thinks that’s good is wearing rose-colored glasses... (sorry for the blunt words... but I can’t evaluate it any other way no matter how I twist or turn it)

pay double for heating than I pay now and from the technology I don't even hear anything. What comes after that is also only conditionally clear. That is simply anything but sustainable.

I believe one must evaluate the matter itself more neutrally and not compare it with old shoes. No one said sustainability is cheap(er). A lot will be demanded from us in the future. And no: that does not mean that I think it is good just because I make the statement.

As long as this is upheld only by us in Europe and Russia/China and all the emerging countries do not participate in climate protection, it will be impossible to stop global warming.