It depends on how close the mountain is to the stations involved. If one end is too close to a mountain a common scattering volume will not be visible to both ends.
We contest from a site about 180m ASL. To the North about 3km away we have 360m hills. There are plenty more hills further North up to 800m. Working Glasgow is hard… but working Edinburgh is very hard as the city sits right behind the Pentlands at 500m. Any contact involves tropo scatter and reflection and some ducting and the signals are very crufty.
Or wait till a plane is making its way North and we use that and get a 30sec to 1min 30sec window of aircraft scatter and have lovely clean S9 signals with cruftiness at the start and end. It’s enough for an SSB contest exchange.
A few days ago, Rick G4XPL/P and I were investigating troposcatter on 23cm. He was on a small hill near Settle (Yorks) about 38km from me on G/LD-058 (Arnside Knott, S. Cumbria) with significantly higher ground between us. Using low-power 23cm transverters and horizontally-polarized handheld Yagis, I could just about hear him on the expected bearing (with Yagi pointing horizontally) but his signal strength went up by about 3 S-points when I also angled the Yagi upwards ~15-20 degrees to the horizontal. This suggests that RF is getting there mainly by reflections and troposcatter.
Of course, TS is much more effective at 1.3GHz than at 28MHz.
If we talk about HF in general, not just 10m, then we come to my favourite propagation mode for local/regional comms hopping over mountains, namely Near Vertical Incidence Skywave (NVIS), and my second-favourite HF band, 60m. NVIS is best using 5-7 MHz daytime, and 2-4 MHz at night.
Use Airscout which will show you the potential aircraft scatter paths.
I use aircraft scatter for 2m - 23cm contacts and do not hear any real flutter from reflections - the signal generally starts weak, climbs to a peak (which can be really strong) then dies almost instantly - SSB or CW
Thanks for the complete!