Good morning-You might want to check this web site for the Oregon State POLICE frequencies:
http://home.comcast.net/~kd6kpc/hobby/s ... police.htm
From my recollection these look pretty comprehensive. The State Police in Oregon used to use a unique 12-code for their transmissions. I don't know if they still do. If you are looking for the State Police on highways the last time I was there they were using two different paint schemes: one was the traditional black and white and the other is a navy blue with a gold stripe.
Moving to VHF was a big step for OSP. For years they maintained low band radio traffic (47.00 type frequencies) because of the exteme distance between the Troopers and the dispatch centers, especially in Eastern Oregon.
Hope this helps.