Only somewhat. Lemmy Communities show up as users when viewed from mastodon, that boost every single post and comment in the community (so browsing it is near impossible, and there is no sorting). Mastodon users can interact with posts (but can’t downvote), and they can post by @-ing the community.
You can’t follow mastodon users or view mastodon posts from Lemmy. I heard kbin had some functionality to do with this tho