Wilfred,
 
Wv> And if he by accident, does choose an existing number in another net, I
Wv> think the ZC should intervene...
 
Yes, but ... a ZC is also just only human, so unless he/she reads the nodelist as if it were the Saturday newspaper, the ZC will never know. Netmail may become totally routed wrong for concerned nodes but then again, unless that is made obvious it will not reveal the true cause.
 
ZCs have a kind of understanding we stay away from duplicate net-numbers. Technically with the current set of ZCs that works, in the past it wasn't always that evident.
 
As for the 310-overlap ... well, I think the duplication happened honestly without an agenda and we can live with it.
 
 \%/@rd 

--- DB4 - Jan 09 2022