said by jbob:
To clarify it looks like the current connection, as in the picture, the working line is plugged into the Test Jack on the NID.
Weird. Usually there is a "wiring bridge" from the test jack to the line module (orange blocks), such that the telco side is connected to the blocks via the "wiring bridge". Disconnecting the "wiring bridge" disconnects the premises wiring. It appears that the "wiring bridge" has been replaced by the wire to the filter/splitter. I am guessing that none of the orange blocks are live.
Wiring bridges in a two-line NID.
The photo is the NID at my mother's house. The eight screws are equivalent to your orange blocks. The test jacks are occupied by the "wiring bridges" from the screws to the telco. Your photo suggests that the line "wiring bridge" has been removed, and the test jack side permanently wired to the premises. I found a diagram which shows these "wiring bridges":
So where is the "wiring bridge" in your photo?--
~Oh Lord, why have you come
~To Konnyu, with the Lion and the Drum