That certainly looks like older dropwire that was then run into the house. The proximity of the power cables certainly could be a source of noise, if there is anything on that ring that could cause it
IF you had BT in to relocate the master to just where it comes into the house, then install the modem close by you could alleviate the possible noise or split it to voice and xDSL at that point, then run both up to the house in Cat5e/6 you could reduce the noise pickup. However, as has been said, if it works, why interfere too much.
If it was me, I would have the master relocated and accept teh cost of doing so, knowing I had removed sme potential issues.
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