In the UK the only contaminated runway condition that can be measured for grip and reported is compacted snow or ice. Thats why you have snow and ice tables in the cockpit.
I have always taken the snow/ice eqv. depth tables purley for use on take-off perf. calculation. And only to calculate if the eqv. depth of contaminate exceeds our landing maximum (25mm dry snow).
For landing we only have the Boeing generic landing data tables, which give distances for good/medium/poor braking actions, although we do have conventional landing data tables for wet runways, which from my perspective are usless with braking actions less than good.
If I was quoted 'braking action unreliable' on finals - I would divert.
Why risk it? Its your neck and licence on the line.
A lawyer will rip you apart when you run off the runway saying how did you know the braking action was not poor?