Hi Brian,
I’ll share some thoughts of mine, I do not intend to squeeze the theme.

“I remain unclear on whether or not a task can be assigned to a user group in general, or if that is the purpose of a user group tagged as being a resource pool.”
Assign a group for a project task should be used for planning purposes only. When you assign a resource to a task, you must expect that this resource delivers the task needs. If you have a group as a resource, who is accountable? That’s why I believe you can have groups only for planning purposes.

“1. if you can assign a user group that is not a resource pool – how does this work? do all users of the user group receive a notification when the task moves from proposed to active? who is responsible for accomplishing the task?”
Do not use groups as team members on project’s execution phase, nobody will deliver the needs.

“2. if a user group is a resource pool, I understand, but have yet to see in practice, that the owner of the resource pool is notified on activation of the task … how do they then assign/delegate? a user? what happens if you try and assign a user that is not part of the resource pool.”
The pool owner is notified everytime his/her pool is added as team member of a project. The pool owner can them choose the best resource to attend the project/task needs based on knowledge, availability and so on. The project owner can add a resource pool resource directly without the interference of the pool owner, it is something that should be arranged during the process mapping phase, this allocation process.
Every resource has their availability based on the amount of effort the project portfolio is consuming, either a group or a user has a amount of hours that can be used in projects. The pool owner can manage the amount of hours of a single user or the entire group. Adding a user out of a pool will consume it’s hour.
There are many others deployments of it, a bunch of Agile reports ready to use, many functionalities embedded in Gantt Chart and so on.
Just some thoughts, good luck.

My best
Carlos

Hi Brian,

We are using only the resource pool. 

I agree with Carlos. We found it to be much better to use from many perspectives: resources management (by pool and not by user), notifications, project management and follow up.

Yaniv