Regarding working in PCP's and breaking down, or 'Tapping' on a pair.
Officially, on 'Crimped' pairs they should be 3-way crimps whereby we can insert a small prong into the unused middle port to check for correct dial-tone, no dial-tone etc etc ......... However, I personally don't know anyone who does this ??
Also, a major problem borne initially out of the bonus schemes they ran years ago (SMT, FRS), and the subsequent implementation of 'Performance Management' our 'Routing & Records' systems are in disarray. Mainly on the D-sides.
So, if a 'Spare' is required to a DP/Joint etc, the systems will present the engineer with what is available, only to find out there are indeed 'Workers' on them.
In times of low work-stacks, which is extremely rare these days, we may be issued with 'Data-cleanse' tasks which means we 'tap out' a DP to cross-reference the current records and update as necessary.
Regarding the 'Screw-connection' PCP's. They only ones I am aware of are PCP100's ..... otherwise referred to as 'Pinned Connection' cabinets. We only had one on our patch which was upgraded years ago as part of our FVR (Fault Volume Reduction) programme. I am surprised to hear there may still be some still in service ??