[smingo]

Someone must have felt very clever when they concluded Erlang would be dimensionless.

  Calls per second X seconds per call = no unit.

But that's wrong. Clearly the number of calls ongoing maps on to lines being used for a circuit-switched network, or datagrams in flight, or whatever. Far from dimensionless.

  Call_starts per second X call.seconds per call_start = calls as the unit

Much more plausible, IMHO.