Adding further details for this one...
More experimentation has revealed that we can deploy printers thru GP to USERS just fine, as long as the policy is configured for an OU or security group containing users.
However, this is not what we need. In our organization, we have users who are constantly moving from branch to branch, from machine to machine. What we need is for the user to have printers installed based on WHERE they are (per-machine deployment) and not WHO they are (per-user deployment). Say if a user has been working at Branch A, but needs to move to Branch B for the day, we want the user to get Branch B printers automatically when they log on to a machine at Branch B. Deploying on a per-user basis is mostly useless to us, except for the group of users who seldom change location.
We have been adding printers to GPOs through Print Management Console with the "Deploy with Group Policy..." function. The deployment "succeeds" in that no errors are thrown during the operation. Running RSOP on a computer within the OU where the GPO is applied indicates that the policy was applied successfully. Yet no printers are actually installed on computers within the OU. Not when the computer is restarted. Not if gpupdate /force is run. Not if a group policy update is pushed from the domain controller. They just don't install.