Wouldn't a split pair show up from the pulse generator they use to identify the lines?
Not sure what you mean by a 'pulse generator' .... but the only way a split pair would show is if the AC Balance result was low on the 'Pair Quality Test', or the engineer manually breaks the circuit down at various places and tests the 'dead pair' for AC Balance.
The PQT test will report the AC Balance for the circuit in its entirety (From the house back to the Exchange), so you could have for example, a 100mtr section of split-pair cable nestled in a 3 mile long circuit, ergo the results wouldn't identify an issue.
Probably the hardest fault to work on, barring REIN, in the engineers remit.
*** Just had a thought - do you mean a 'Tone generator', to identify the line ?? If so, this unit performs just one function and one function only, to inject a low frequency tone into the circuit that we can identify with our amplifier. It has no indication as to whether fault is present.