Is that just they ban sharing your credentials with the neighbours. If you could set up a ptp link (id say Omni on sisters house and a directional one at the p

Is that just they ban sharing your credentials with the neighbours. If you could set up a ptp link (id say Omni on sisters house and a directional one at the parents) as a bridge from parents to sisters house. 2Km with LOS is trivial to achieve. As your effectively bridging the two houses any host in the parents house would be part of the same network and be seen as such. As in the US the phone company's responsibility ends at the demarc trying to stop how your internal wiring is configured seems impossible:-)