[cisco-voip] Looking for suggestions/options on a 911 problem

[Dark Fiber]

Trying to find the simpliest way to resolve an issue.  Dealing with a
CM setup that has 5 locations, all phones are configured with a device
pool specific to the location they are in.

The phones are all in the same general CSS however and the line on
each phone is in the same partition and CSS as each other.

So the only thing that defines the location of the phone is the Device Pool.

I don't think I have a way to specify what gateway a particular device
pool should use for 911 calls can I?

I think I could do something if each locations phone was in a specific
CSS maybe?

The locations have some older 3745 gateway devices not being used
anymore but they have a live PSTN line connected, the idea was to send
911 calls only out that old PSTN line but with the phones all being in
the same CSS and stuff I just don't see an easy way to accomplish it
based just on device pool.

Am I missing anything?  Or does this assumption seem right, and I will
have to probably put them in specific CSS's based on location as well?