To answer my own question about harvesting ice fog, in areas downwind of the SLC airport, their cloud seeding efforts (cryogenic CO2, in the day, and silver iodide at night) cause the ice crystals to coalesce into larger particles which then precipitate to form a thin layer of fresh "snow". Ice fog will also coalesce around particulate pollution and precipitate, helping to clean the air. The ice fog itself is sometimes erroneously counted as particulate pollution, causing PM 2.5 levels to spike.
I suppose, theoretically, that ice fog could be harvested, but in a sense, it harvests itself in a daily cycle of sublimation and precipitation.
It has been my unprofessional observation that ice fog requires snow cover, even just an inch or so, for it to form in a Winter inversion (an exception being the Great Salt Lake, which sublimates supercooled water into the freezing air above it). It is that daily cycle that maintains both the ice fog and the snow cover, until a strong enough front comes through to uncap the valley and sweep the fog out.
There could be ways to harvest ice fog, but I am not sure it would be economical.
For those unfamiliar with Winter inversion related ice fog, here in the Intermountain West of the US, the valleys can form ice fog from water vapor that is not allowed to dissipate into the atmosphere by a strong inversion layer.
Temperatures in the valley will eventually come to a day/night equilibrium well below freezing (along the Wasatch Front in Utah, that temperature is often 14 F. It can be higher or much lower, depending on the location, elevation and conditions). Above the inversion layer, it is usually sunny, warm and dry. Temperatures at the ski resorts can be in the 50's. Inversions can last 6 to 8 weeks. They are often associated with droughts. The length of the day also determines whether an ice fog will develop. It needs short days...probably.
While an inversion is generally stagnant, there can be considerable localized air movement, often influenced by pressure variations, differences in fog density and air temperature, topography, air and surface traffic, and I am sure there are a few more. (I have wondered if an array of large vortex cannons down the middle of the valley could induce enough vertical circulation to disrupt the inversion. Similar to bubble aerators used to clear stagnant ponds and lakes.)
Gratefully, we have been having more rain in the valleys in the past few years, so no ice fog. I sometimes miss it, it has a peaceful ambience, but then I get over it. It is nice to see sun without having to drive several miles uphill.