Hi kookaburra,
I'm a little bit up north of you in Vancouver, CA. Similar weather, I imagine (though we are somewhat sheltered from the Pacific by Vancouver Island) and a similar commute (4.7 miles each way). Anyway, a few winters back I bought a Gerber hi-viz EMS coat (w/removable liner). It's similar to the ones sold by alertshirt (specifically the ANSI class 3 bomber), very good quality, but a terrible coat for Winter commuting by bike.

I'd intended on using the coat only for the worst weather conditions that might make the use of my e-bike (it's AWD-ish, for snow and ice, not that we get any here.) a logical resort. Only problem is that on the odd occasions that I do haul my e-bike out from retirement I find myself trying to meet or exceed the electric motors output resulting in mad high-speed sprints that aren't conducive to a cool and relaxed riding style (This riding style carried over to my non-electric daily commuter which completely rules out using the Gerber EMS coat for commuting. I'd die from heat exhaustion or an MI or some damned thing). The coat is a little too bulky for my tastes, not very breathable and more often than not I'd wind up as wet inside from condensation as outside from the elements.

Coats like these aren't designed with bicycle commuting in mind. I've found that, for myself, going with more bicycling specific clothing for my outer layer(s) works much better. If hi-viz is required I bring along a hi-viz vest or sash. The shirts are good though, really like those, but I'd pass on the road crew/emergency services coats and go with a good, single layer, bike specific, wind and water proof jacket with the usual assortment of pit-zips and such then layer up underneath as necessary.