does this remove command finalize the move?

does it remove a soft delete from the source database?

The documentation tells you what it does.

https://technet.microsoft.com/en-us/library/jj219167(v=exchg.150).aspx

what are subscriptions?

I don't know, but whatever they are, they're deleted!

I'll ask and post back here if I find out anything useful.

I've been told the following.  For on-premises Exchange there aren't any subscriptions, only move requests.  Inter-organizational moves can have other protocols such as IMAP, and those would be considered subscriptions.