Question about dormant second line

The previous owners of our flat had a second phone line installed in a back room.
We didn't need this line so didn't take it over. The line doesn't have a ring tone at the moment.
This cables are much newer than our phone line and it has a modern socket. Our cable and socket are old in poor condition.

I have a couple of questions I hope you can help with.
Our phone line is connected to a cabinet quite a long way away but there is another just around the corner (about a third of the distance). Is it possible that the newer line could be connected to a different cabinet?

if it is on a closer cabinet, would it be difficult/expensive to get our phone number transferred to the new line? (I am thinking about FTTC here)

If it is relevant, line rental is currently with BT.

It is possible that your hope is true, but unlikely.

Trace where the wiring for this other line goes, odds are that it vanishes into the same bundle as the existing live line.

It is 99.9% certain that the redundant second line is routed via exactly the same cable run back to the same cabinet as your first line.

Best bet, order your FTTC service, and ask the installing engineer if they can provide service via the old second NTE. They will be more than happy to do this.

Transferring the number is easy, dunno about the line quality though.

I traced the two lines. The old (active) line runs to an old-looking round box and the newer (dormant) line runs to a newish grey square box on the wall.

A separate cable run from each box in to ground.

To complicate things, there also appears to be a cable linking the two boxes so I am not sure what is going on!