We encountered the folowing problem in our JIRA installation, the inability to subscribe another user to a saved filter.
We are using Crowd as backend, which is connected to AD/LDAP and we do have a strict policy on not creating crowd accounts at all. So we sync all accounts from corporate AD, where we obviously we do not have write access.
In order to overcome some limitations on Jira we used a trick to convince JIRA (or Crowd) to see some corporate mailing lists as users. This does allow us to assign tickets to some special Exchange mailing lists.
Now, the problem is that we were not able to assign filters / subscription to these users. Obviously because these are "fake" users, we cannot login as them and as far as we know, JIRA does not allow you to subscribe somebody else to a filter.