ChristiaanJ:
Where I come from (admittedly some time ago), channel A and channel B software were maybe not actually written by two different companies, but definitely by two different teams, using different compilers, etc. etc.
My knowledge on the subject is admittedly 10 years old, but as I learnt it that statement is 100% correct. In addition to that, when the code is reviewed if even the slightest correlation in the two methods is found, the code is rejected and one or both of the teams has to rewrite it from scratch using a different methodology.
Pacplyer, I know you're aware of this but I can't emphasise enough that real-time and embedded software engineering is a completely separate discipline from application development, with a completely different definition of 'finished product'. I'm groping for an analogy here, so bear with me, but if application development could be described as an engineering discipline like building an F1 car (lots of whiz-bang features and cutting edge technology, but expected to only be used for a short period of time and to have frequent problems), then real-time software is more akin to engineering the Forth Bridge (old and proven technology, redundancy up the wazoo and designed to last for centuries if necessary).