Mixing dubbed shows is many ways easier than mixing original language dialogue and ADR, because the dialogue is clean, has little background noise, and is at a more or less steady level throughout. While here I won't go into details about the art of mixing, I would like to mention a couple of specific points. Distribution reps who have little familiarity with mixing may not be able to evaluate the quality of the work of a dubbing house, and choosing a studio based on reputation alone can leave one unpleasantly surprised. I have worked with a number of dubbing studios staffed by mixer veterans whose knowledge of the art of mixing dates back to the days of their apprenticeship that took place over 20 years ago and has progressed little since. For example, they might use a single severely EQed filter for both sides of a cellphone conversation, wash everything in reverb, and apply generous compression until the noise floor becomes a loud hiss and every lip smack - however negligible under normal circumstances - is audible. To avoid mediocre work, a potential client must listen to examples produced at a given studio and compare the quality of the original sound with that of the foreign language mix. While the two will inevitably sound different, this is nevertheless a good indication of how carefully the mixer has paid attention to the original and how capable he or she is of reproducing it.
Mixing documentation
Dubbing mixers often get notes from the original studio describing the effects' parameters and sound treatment details. Those may include plugin settings (or screenshots of plugin parameters), sometimes even pre-automated sessions containing all necessary effects.
Is a mix produced by the dubbing studio as good as a mix done at the original studio?
From the production side of things, a question often asked is what are the advantages and drawbacks of mixing at the dubbing studio versus at the original production studio.
At the original production studio:
Pros: Familiarity with the project
Cons: Communication difficulties
if a line is forgotten for example – usually goes back & forth between several intermediaries (the international distributor)
time will have elapsed since the project was last worked on, and may not be worked on by the same crew, hence the pro of familiarity with the project will not apply
unfamiliarity with the language – this can throw people off
At the dubbing studio:
Pros
Meeting distribution deadlines
Efficient communication between those responsible for the project
Cons: May lack in detail and refinement compared to the original mix