If we co-host can I share the attendee information list?

No. We're really careful about what we do with our community/customer's data and we don't want another random group having it to message or potentially spam. It's safer that way. If they need something give them the names and companies but not the emails. (This applies to sponsorships as well... i.e. we never, ever, share our mailing list or database with any other third party - see the  sponsorships doc for more help).