Well, the "one more technique" did not work;
instead of AM,BEN, etc.,
I tried <ParameterValue><Name>pg_list</Name><Value>AM</Value></ParameterValue><ParameterValue><Name>pg_list</Name><Value>BEN</Value></ParameterValue> etc.
I'm out of ideas on how to get this to work dynamically. So ...
1. In VS, I ended up setting Default Values on all parameters up to and including PGs and Employees, then deployed it to the RM server.
2. Created a linked report from it.
3. Went back to the linked-to report, then Manage > [report] > Parameters, cleared the "Use default" checkbox. This is to prevent the report from running automatically when a user clicks on it; some of these reports take 5+ minutes to run, and it would be nasty to force the user to click cancel if they didn't want to run it for everyone.
4. Created the subscription on the linked report, where I set the "Source of value" on the two parameters in Report parameters to "Use default value", which I hope will be refreshed with the latest values each time the subscription runs. If that does not prove to be the case, I'm screwed.
This solution works, but is not stable - changes to the linked-to report might break the linked report and/or the subscription on the linked report.
MS, IMO, has fallen flat on its face with this - once again, they are blind to, or don't care about, obvious capabilities & features that, because they are absent, cause customers to do a lot of head-banging to implement some other way. If they did not have us by the short hairs, they would quickly go out of business.
thank you, beth