Sure, the ISP signing up the second connection can't see what name the first ISP put it under anyway so there's no way to check.

Yes.  When I lived with my in-laws they had a Spark connection on one port, and I had my Orcon connection on the other port.

those are sounds great

Just putting it out there that Northpower can't/won't activate the second port if the customer name does not match that of the primary connection.

I ran into this situation recently when a business operating inside the premises of another larger business wanted to get their own fibre connection on the second port of the existing ONT. Northpower advised that both connections would have to be in the same business name otherwise they could not proceed with the 2nd connection.

Other LFC's do not have this restriction AFAIK.