The Kifissia-Piraeus electric railway (ISAP) and the tram will also be out of service for the same reason.
Employees had argued that they work under different conditions to regular civil servants and should therefore be exempted from the unified pay scale.
However, they were informed on Thursday by government officials this would not happen.
“There can be no exceptions,” said Development Minister Costis Hatzidakis.
“The government cannot back down on this.”
It is possible the strikes will continue over the weekend.
Bus and trolley bus employees are due to meet on Monday to decide on possible action.