The price of the CP ticket or pass is calculated according to the number of zones you go through.
In the case of stations that are on the borderline between zones, you only pay 1 zone for your ticket or pass, but you can only travel between these neighbouring stations.
For a journey between Mercês and Rio de Mouro (neighbouring stations in different zones) you have to get a 1-zone ticket. If you want to use another station in the Mercês zone or the Rio de Mouro zone, you have to pay for two zones, but can then travel throughout the Sintra and Massamá-Barcarena zones.
You can use the ticket on any journey on the Sintra, Azambuja, Cascais or Sado lines so long as the journey covers the number of zones you have bought. For instance, a 1-zone ticjet canb take you from Sintra to Algueirão, Cascais to Estoril, Azambuja to Carregado or Praias Sado-A to Palmela.
The pass covers a fixed route. The route is valid up to the end of a zone. (For instance: if you get a pass between Cacém/Amadora, the limits are Rio de Mouro-S.C.Damaia (2 zones)
The Lisbon zone has a fixed price.
CP Services: Lisbon urban trains