For example: You can choose the standard livery without the logo as a template, with the template you can add other things etc. You can use one of your own liveries as a template from a other train.
That wouldn't be possible due to licensing issues. Technically this is already possible if you're working on the same type of rolling stock, you can just copy the livery and then work on the copied version.
I made a typo, I mean the standard livery without the logo on it. But you can't copy a livery on train A to train B.
