I had a quick look around and as far as I can see there is no evidence what so ever for the use of e.g. electrotherapy and erb's paralysis. The discussion is if stimulation of e.g. a muscle will contribute to the restoration of the connection between the central nervous system and the target e.g. muscle. The assumption can be that it would help but on which grounds? One can argue that a signal (stimulation) would help to lead the way. but the signal could also trigger the opposite reaction; e.g markers for a disfunction (hormones and neurotransmitters) are not send and hitero no response for repair.
If there is any research which is sound please let me know.
The best remark so far is that electro tehrapy can only be used if the therapist has in fact a marker(s) for stimulation of nerves in a baby, also we have to understand that the nervous system of a child is fully developed at the age of 6-8 years old (for that reason there is a reluctance on putting a diagnose on e.g. CP)
The use of TES is at least in the information provided not related to e.g erb's paralysis but to e.g. CP which is a centralised problem with bodily symptoms.