Good PCB Design - Single Power Plane with 2 Power supplies (+ve & -ve)
Yes and No.

The problem with separate ground plane, it can become very complex to understand the current flow, and most of the time it is better to have a single ground plane.

Separate plane can be useful if you have filtering of the power and a lot of digital going on, but a lot of care needs to be taken.

The planes shall connect underneath the IC that has analog / digital, and you shouldn't have any trace going between the plane, at any layer. If you need trace going through from analog to digital plane, they should be above (or below) the connection between the two ground planes.