We already have a feature ticket to extend the CBSubs emails with additional substitutions, including the one you're wanting to use, but this isn't an easy implementation mainly because those emails act on subscription state changes and don't include the basket which is where the invoice details come from (a basket is an invoice in CBSubs).
As for CB Auto Actions no that won't be possible as that's just not how it works. It doesn't have a clue what your trigger is, the variables of that trigger, or what to do with those variables. It's basically just a state machine waiting for an event to act on. So no it can't do what you're wanting as it doesn't know CBSubs even exists let alone that it has substitutions. You have to use PHP if you want access to that information.