Hi R,
I’m not 100% certain what you mean by this particular question:
Past this plugin on all themes?
It seems your main question is whether or not the new theme you try out will work with The Events Calendar PRO. The short answer to that is yes, as long as the new theme is a WordPress standards-compliant and well-coded theme, Events Calendar PRO should work fine.
If you’ve made customizations in your theme to The Events Calendar PRO, however, then you will manually need to port those customizations over to your new theme.
Let us know if these answers are at all helpful, or if you have any other followups questions or concerns.
Thanks!
George