> that usually requires either consent and active participation of previous user at the same address or proving that you have legal right to use the property.

That's the key. Where I live, it only takes online applications to sign up with power companies and telcos, if infrastructure is already in place (cables laid, power meters installed, etc) and it's not associated with any active contract. After sign-up, services are remotely turned on and kept on as long as bills are being paid.

It's not up to service providers to police property rights. They own or have rights to infrastructure leading up to the final junction box and what happens downstream is not their business.