Using of RF transcieivers to communicate over 230VAC powerline
This question assumes that connecting an RF signal to a power line does not convert the power line into an antenna. The power line will become an antenna and you will find that neighbors will in fact interfere with each other.

It's also quite probable (in some cases) that powerline comms will extend their range to neighbouring houses.

So, what you need to do is think about using some kind of protocol that can allow neighbours to interfere with each other without this necessarily causing an operational problem.