EX2013 Proxying OWA for EX2010 mailboxes and required SAN's for SSL Certificate from Public CA?

Hello -

We're currently on EX2010 with a Kemp Load Balancer using an SSL certificate from our internal CA.

For the EX2010 cert we added all the CAS servers as SAN's to clear up certificate errors when client computers download the OAB etc.

OWA is up & running for LAN connected computers.

Now we have a desire to publish OWA on the internet.

So we need to buy an SSL cert from a public CA.

We also have an EX2013 deployment on the horizon, so we need to buy a cert with EX2013 names (mail.domain.com & autodiscover.domain.com)

While we're in a migration state, EX2013 will proxy OWA requests for EX2010 mailboxes.

Will the cert from the public CA also need to include the SAN's for each of the EX2010 CAS servers?

Thank you.