[ElevenLathe]

Right but I meant my point to be that the people on call don't have to be literally the same people developing the application code. In fact, they never have to communicate at all, because they can coordinate at arms-length with a well-defined software interface.

Edit: I missed the part where you say the Heroku customer has their own on-call team. IME this is not true. The whole reason to use a PaaS like this is to avoid having an Ops team. Sometimes orgs outgrow their PaaS and keep using it anyway, but this isn't necessary, only a historical artifact. These orgs would likely save more money and get a better result by going with normal IaaS or racking their own servers and, in fact, are probably actively switching to that model.