Mercenaries: cannot be critted vs guaranteed crit

So, I’ve been wondering for some time: what happens when an effect that causes all attacks to crit (Diablo’s Apocalypse, Brann’s Summit Campfire, Trigore’s Regrow Heads) or has guaranteed critical damage (Kurtrus, Vashj, Slitherspear, Rogers have these effects) targets a merc that cannot be critted (Saronite Armour or Mutanus’s Irridescent Necklace provide that)?

[UPD]
Finally got a chance to test it in PvE… In particular, Reflex Shot did not crit against Saronite Armor.

[UPD 2]
Forgot to add another example: bleeding, which no longer crits due to role advantage after some patch, still does if forced by Brann’s Summit Campfire. Still not sure whether the ‘glowing red border’ effect, forcing critical damage from all sources, affects Saronite Armor or Mutanus’s Irridescent Necklace. Perhaps one could test it against the Babbling Book…