Back, with nary a comment on the long hiatus!
Ok, so I don't think that theological study and religious activities share a common basis. I think they are two different human activities that come together with the glue of culture.
It's probably a pretty common belief that religion is theology put into action. The corallary is that theology is the theoretical underpinning of religion. If it isn't that, what is it?
Let's try asking this question: what would theological study in an atheistic reality hold in common with theological study in a theistic world?
The answer: speech and writing. Theological study is about developing propositions about God; if God does not exist, the activity of developing propositions still exists. Propositions take the form of speech and writing. Also known as symbolic representation.
In both atheistic and theistic worlds, theological study is about symbolically representing God and beliefs about God.