AD Attributes after Exchange 2003 uninstall

Hi,

i've a Customer that need to uninstall Exchange 2003 organization due to Google apps migration.

The question is : what's happen to the AD Attributes added to Schema by Exchange installation, like : 

ProxyAddreses

MAIL

I Verify that if i delete a mailbox from a user, the MAIL attribute, is deleted from user.

The Customer have few application (like CRM, JDe EnterpriseOne and so on) that use this attributes for Single sign On or many other purpose.

So the problem is how to maintain this attributes after the complete removing of Exchange 2003 Organization.

I think that an Export and import (after uninstall) is a possibile solution if the attribute are still availble on the schema.

Thanks

Marco