I'm not sure this addresses the deliverability issue. There seems like a more fundamental question of whether using different email addresses will boost engagement and keep deliverability strong, and I too am interested in what other people have seen when testing these changes.
Some of us already use Litmus at our firm, but it's not as widely adopted as I'd like. However, we recently started working with a client who uses Outlook heavily and got frustrated when their former firm wouldn't fix issues that kept showing up in their inbox.
Using Litmus, I was able to quickly show my co-workers how we could fix those longstanding issues, and proved that Litmus could be a powerful addition to their own workflows.