I find (for Brit engineers) the following values: 1. heal action 1,6; 2. heal action 0,5; 3. heal action 0,525
Which are 1. base repair; 2. vetted squad, 3. Heavy sapper upgrade.
-For a 5 man squad, this would lead to repair speeds of 8, 10,5 and 13,625, respectively.
The smoke repair ability has a repair speed of 11.
-> total speed of 13,625/squad; 27,25 for 2 squads + 11 ability repair = 38,25
OKW:
Pioneer repair speed: 2; vet2 bonus 0,75; upgrade bonus 0,5; combined vet+upgrade bonus (apparently there is one, I did not know this before) 0,1875.
-> Makes a total speed of 13,75 per squad, or 27,5 for two. Plus mechanized HQ repairs that I don't know about. Or approx 27 without the shady combined bonus.
I don't find anything about the base pioneers, so maybe they're the same?
OST: uses the soviet repair ability
repair speed: 1,6; vet2 bonus: 1; (there's also an upgrade bonus of 0,3 for breakthrough package, but I'll leave it out due to doctrin)
-> Makes a total speed of 10,4/squad or 20,8 for two squads.
Now, post patch, OST and SOV get additional 0,3 per model, leading to a max speed of 11,6 HP/s and 23,2 HP/s for two squads.
Now it's not realistic to max everything out, but you can do the maths from there yourself.
To sum up, max repair speeds per squad:
SOV: 11,6
OST: 11,6
UKF: 13,625
OKW: 13,75 (plus potential repair engi upgrade on T2 with 9 HP/s in total)
USF: Don't know, but they use different mechanics anyway, so harder to nail down.
And before the discussion takes off:
Another thing to consider is the tank upkeep regarding repairs. In general, Allies have higher chances to get penned and thus need repairs slightly more often (there are exceptions of course). And then there is pop for the engineer squads. For OKW it's usually a bad idea to go for two engineers due to high cost and maintainance.