I have tried now with many different Cubes including old blacks, newer blacks, and one orange cube to upload Rally points thru the telemetry modem. It fails everytime.
I am only able to upload rally points thru USB connection. But after disconnecting Mission Planner does not show the rally points any more. They are in the memory of the Cube but they do not show in Mission Planner. I have tested that they work but it is very inconvenient not to see the rally points in GCS.