1. Active Roles does not look for SCP to detect if Exchange is installed or not.
2. A LDAP search is made (ObjectCategory=msExchAdminGroup) for the msExchAdminGroup Object for the Administrative Group whose site folder Server you want to check (CN=Administrative Groups,CN=Organization,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=Domain,DC=com). A list is maintained containing the admin groups (depending on number of side by side Exchange Servers installed) and the edsaIsMsExchangePresent value is updated as true if there is at least one value in the list indicating that Exchange is setup and has at least one store (mailbox DB).