The tool the LBS used was probably something like the old Kingsbridge fixed cup tool, which is a shop version of Sheldon's BB&N (Big Bolt & Nut). I have always been glad that I bought mine decades ago, as it has never failed. Be careful if using an adjustable wrench held tight against the BB, as many of these have a taper to the jaws and are difficult to keep fully engaged with the flats. I have used the Kingsbridge tool to get out frozen adjustable cups. I've had frames handed to me where the mechanic can't get enough purchase with a pin spanner to get the adjustable cup out. What I'll do is to pull the fixed cup by putting a flat wrench on it (if I have the size), and holding the wrench against the BB by adding a Regina freewheel body, held in place by a crankarm bolt and large washers. Once I get the fixed cup out, I'll use the Kingsbridge tool on the adjustable cup. I've had to use a cheater bar to get the tool clamped down tight enough, but it's never failed or destroyed the cup.

Long end goes into the BB shell. You turn the tool on whichever side will turn the cup in the required direction, clockwise.