Do you have any recomendations as to how I can impliment a work-around for trying to query CAs at the forest level, rather than at the domain level ?what type is your CA? Enterprise CAs are registered in the configuration naming context and are forest-wide services. The code looks for any Enterprise CA in the forest. There is no domain-level lookup. Enterprise CAs are retrieved by calling Get-CertificationAuthority command.
Standalone CAs are not registered anywhere in the Active Directory, so the only way to reach it is to use Connect-CertificationAuthority command.