Both Montana and California are members of the Drivers License Compact meaning that they share information with regards to moving violations their licensed drivers receive out of state. It is unfortunate that the MT officer did not understand how information was exchanged and that when he turned in the ticket information the Montana court system would send the information to the California Department of Motor Vehicles.

According to the California Department of Motor Vehicle's violation point assessment listing, an out of state speeding ticket is a 1 point offense on your CA driving record.

In California, you need to have traffic school approved by the clerk of the court or another judicial official in the country which your ticket was received. Since your ticket did not go through a CA court due to being from out of state, it would not appear that you could take a driving course to remove it from your California driving record.