Just a hunch -- the switchboard might have been co-located at or next door to the bank at 102 Fremont. That would put them just a stone's throw from the railroad depot (where Union Plaza would be), and that would tie in to the telegraph / telephone poles and wires that ran parallel to the RR tracks.

(The bank may have funded the loan for the telephone exchange in LV too. And having an "in" with the phone company has its privileges.