If you fit another manufacturers mcbs into a distribution board or consumer unit it will negate any warranty on the product. If the product is out of warranty then should anything unfortunate occur both products manufacturers will state that the compnents were not designed to be used with each other and liability will rest firmly on your shoulders. The fact that mcbs are manufactured to the same specification does not come into it, all cars for the UK market are designed to the same regulations but would you put parts interchange parts of their engine and if you do make modifications you have to notify your insurance company and normally the premiums go up.
At the end of the day it's up to you, but I know what I do. Yes there are times when products have been used when the other manufacturer is either not available or no longer made however what I will say is that I spent some years working for circuit breaker manufacturers and not only am I aware of what the manufacturers response to interchange will be but also have a good knowledge of which lesser manufacturers use which tooling etc. formally used by the major manufacturers for now obsolete ranges and also where some products come off the same line in China with different branding.
All I will say is be careful what you do.
