Add "Subscribed to emails list" Criterion to Advanced Search
Currently, the only way to find out if members are subscribed to an email subscription list is (I believe) to export the membership list and look at Subscription Source.
There should be an Advanced Search criterion "Subscribed to email list" which allows checking any of the email lists.
(The checkoff "Subscribed to emails" in the Email preferences criterion refers to email blasts, not email subscription lists.)
Walt Bilofsky commented
I see that it is available in Contacts Advanced Search but not in Members Advanced Search. It looks like most of the Contact fields are available in both. This should be added.