Hello Newark pros!

I have never transited through Newark before, but will be doing so next month. I have a United flight from TYS-EWR arr. 1pm, then a 7-hr layover until my 8pm flight EWR-MAD. Best I can tell at this time, it looks like both flights will use Terminal C at Newark. However, I am a Priority Pass member and would like to pass the long layover using one of the clubs (preferably the Air Canada lounge in Terminal A or the Virgin Atlantic Lounge in Terminal B). Will it be possible for me to access one of those? One thing to note: my flights are separate vs one reservation, so at some point I'll have to go landside and re-check. I'm mainly curious whether I can: a) move between terminals airside once I'm checked in, or b) check-in and go through security in a different terminal than I will ultimately depart from. Finally, I don't know if it matters, but I have pre-check.

I've looked for an answer to this online, and can't seem to find anything definitive. The only thing I can seem to find is an EWR map on the United website showing that there is airside transit (bus) that stops at all 3 terminals. But I can't seem to discover for sure whether it's limited to certain passengers. Also whether all parts of the B terminal are accessible airside, or whether it's divided and separate.

Thank you so much for any help you can provide.