I was just out at Mount Hood 3 weeks ago and the only thing I got was Timberline Lodge using the CloseCall feature. Well, that and a lot of the local sheriffs and public safety frequencies along the route from Portland. I was hoping to find some of these same frequencies you mention as well as any frequencies that might be used up near Multnomah Falls and other parks in Oregon.
Multnomah Falls is in the Columbia Gorge NSA, administered by the USFS. Mount Hood is in the Mount Hood NF, administered by the USFS. If the USFS does have a law enforcement presence, it's going to be pretty minimal. A lot of the work falls onto the shoulders of the applicable Sheriff's Office: Multnomah County SO (Multnomah Falls), Clackamas County SO (west side of Mt. Hood), Hood River County SO (east side of Mt. Hood). Also, in Oregon (AFAIK), the SAR responsibility falls onto the Sheriff first and foremost.
Think we have some SAR folks here on the boards that can probably give better info.
Ore. State Parks have a couple of radio channels in use locally at various parks, but don't believe they have a statewide network. The rangers are not LEOs (though I believe the state was considering it). Law enforcement is going to instead be from OSP or local agencies.
WA State Parks have rangers that *are* LEOs (as does CA).
So, you could wind up with an accident on I-84 in the Gorge or a wildfire that gets a response from the USFS, the local fire department or fire district, OSP, ODOT, and the local Sheriff's Office. There's not any one single agency that handles it all.