I think we mary not incorrectly be understanding the following DMV statement.
A nonresident owner may operate a vehicle (other than a commercial vehicle) in California until he/she accepts gainful employment in this state or establishes residency in this state, whichever occurs first, if the vehicle is registered and displays valid license plates issued to that owner by the foreign jurisdiction where he/she was a resident
If you come to CA and look and accept a job then you've accepted gainful employment. However if you are working for your employer in another state, in this case OR, and they send you on assignment and you have no plans to make CA your home then you've not accepted gainful CA employment as you still work for your out of state employer.
I tried to contact the DMV Friday but the return call times were over 2 hours and I had too many things to do to wait for a call. I'll try again on Tuesday.