Using concession bus passes for cross border bus journeys between our provinces.

[swt class 450]

Just a quick question i have always wondered about using concession bus passes for cross border bus journeys between our different provinces (England/Scotland/Wales).

Am i correct in thinking that all English/Scottish/Welsh passes can be used on cross border services as long as you have either boarded or alighted in your province of your pass (ie they are not valid for travel entirely within the other province)?

So for example all English passes can be used to travel on any cross border service in to Scotland or Wales as long as you have either boarded or alighted in England? And then all Scottish passes can be used to travel on any cross border service in to England as long as you have boarded or alighted in Scotland? And then all Welsh passes can be used to travel on any cross border service in to England as long as you have boarded or alighted in Wales?

Is this correct or is it more complicating than this?

Many thanks.