Sorry this has taken so long for me to get back to, I was out for Christmas vacation.
You can mirror between any of the EF-Series and E-Series controller, so yes it is supported to mirror between an EF560 and an E2800. A new document describing mirroring between the newest controllers, with the new System Manager, and the older controllers still using storage Manager is planned for release in the second half of January. The title will be SANtricity 11.40 Mirroring. So you should be able to locate it on netapp.com by the end of the month.