Can anyone tell me whether or not an engineer can check to see if there would be any Infinity speed difference between the 2 lines, from the fibre cabinet to the property?
Not without installing service on both lines and testing it out. Some tests might show up line faults, however they can be repaired. Line performance can ultimately only be checked with service.
It is possible to do a pair swap - this was tried on my lines when I had a fault. The PSTN/Infimity line was swapped with the ISDN and then reverted.
M H C
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