Find WordPress sites hosted by specific hosting provider

I’m looking to potentially upgrade my WordPress hosting to improve performance. I’ve read through How to find web hosting that meets my requirements?. However, before moving my site to a new provider, I’d like to "test" the hosts’ performance prior to signing up.

I know that it’s possible to lookup who hosts a particular domain, but are there any tricks to doing this in reverse? I.e., is it possible to look up what domains are using WordPress hosted by a particular hosting provider?