Not sure about how EventPress works with MU as I’ve never tested—but anyone author and above should be able to create events. There’s also a special role called ‘event_creator’ who just has event creation capabilities and nothing else.
@kunalb Yes, I found in wp.php, but don’t know what to do with this part. There aren’t any settings for EventPress…^^
Ah—you’ll have to use wp-admin’s backend here—the user’s section where you can switch between author/subscriber/admin etc. There’ll be another option for Event Creator there.
@kunalb That’s what I can see on dashboard:
Events: Create new – Event tags – Event categories
Registrations: Registrations – Create new
No more…. nothing about permission… no new field anywhere…
Just read the complete thread again—are you looking for how to grant all site admins a way to edit events (which should be there—but as I’ve never run EP in MU, I have no idea); if you’re just trying to grant subscribers access to editing events you can change their role to Event Creators in wp-admin/users.php.
Yes, all site admins should be able to create and edit events… 
@kunalb O_o… the fault was located between my ears… all the time it works and I didn’t see it. It’s quite clear: A site admin who isn’t user of the main site can’t create events there. I forgot to make them to users. Sometimes it is so easy… Sorry for that.
@chaoti there is a plugin called Multisite User Management (http://wordpress.org/extend/plugins/multisite-user-management/ ) that allows you to automatically assign roles so that every subscriber is assigned to the role on a site in your network you choose. I use it so that every user who subscribes, regardless of which site on the network they subscribe to, is a “subscriber” on the main site.
@kunalb I’m just starting to test my site, and your plugin looks promising. Thank you for all your work.
@chaoti Whew. Getting capabilities working right the first time was pretty tricky—thankfully this means I don’t have to debug it.
@irishfan24 Thanks! Currently considering some major refactoring to reduce bugs and improve security/theming issues. Let’s see what I come up with in a few months.