"North Bay Sub" wouldn't be that descriptive since there are lots of different railways in North Bay. I suspect that's why railways are usually named after a community near the middle of the line, such as
CN Grimsby (Hamilton-Niagara)
CN Kingston (Toronto-Montreal)
VIA Alexandria (Ottawa-Coteau)
GO Oakville (Toronto-Burlington)
GO/CN Guelph (Georgetown-London)
CPKC Galt (Toronto-London)
CN Dundas (Burlington-London)
CN
Bala (Toronto-Capreol)
So if they were to rename the ONR segment of the Newmarket sub my guess is it would become the ONR Huntsville Sub.