Scene timelines are only available (to use Start Timeline, goToTimeInTimeline, etc )for the particular scene they are created. If you want to manipulate these timelines from outside the scene it is in then you can use the "Custom Behaviour" functionality.
In Scene 1, I have a button that has a Mouse Click behaviour. Before I assign the action I create a custom behaviour in the scene I want it to effect. (Scene 2 for example) In this custom behaviour I add goToTimeInTimeline and choose my timeline and time. I also add Start timeline because I want it to start playing from that point immediately. Note: you don't have to add jump to scene as it does that automagically.
Now that I've created my behaviour I can now go back to Scene 1 and assign the action "Trigger Custom Behaviour" and choose the behaviour that I so eloquently named "moveToTimeAndPlay"
Custom Behaviours are found below all the actions in the "Scene" Inspector
After clicking Add Behaviour I am presented with the following where I can name it and choose the actions just like any other built in behaviour.