Do you know if there is any interconnecting linking to the Etihad rail from the metro.

This is Riyadh Metro in Riyadh, Saudi Arabia.

From the news sources here it is mentioned that connection to Saudi and Oman will be connected with the UAE

There’s a Gulf Railway project to connect GCC states. Each country is responsible for its section, and the UAE has finished its part of the project, and a connection with Oman has been agreed on and is under construction.

For Saudi Arabia, its section of the railway is the longest but not a priority as it passes through the sparsely populated east coast, and instead it is prioritizing linking Riyadh to Jeddah. It will eventually be built, but no official due date from Saudi Arabia.