I am sure they do escape elsewhere Australis but it seems to be only you Australians who whinge so much about snakes being anti hybrid (and by whinge I mean whinge more than us pomes) and stating that it is the hybrids that will cause the problems to you native snakes when they escape.
In addition to hybridisation should you also not be looking down your noses at line breeding as this in time will result with you having snakes that also look a million miles away from their natural form. Many people say that so and so snake is a 'specific locality' but due to the fact that it has been selectively bred by the best looking of its species (which again is not what the snakes in question would go for as they are just up for a good old mating session and the females pattern is irrelevant) it generally looks nothing like its true form (but however does look good).
So in addition to hydrids should you also be now bullying the keepers who selectively breed?
You should face it, you may not like the keeping / making of hybrid species but you are fighting a loosing battle. As time progresses you will find that most snakes kept in captivity will be far larger and more attractively patterned than their native counterparts.
ps. you will also find that the majority of Australian snakes smuggled out of Australia is by Australians. You will also find that the majority of it was captive bred too such as the albino darwins etc etc
Apart from the generalisations and resulting anti-Aussie feeling you seem to be expressing i agree with most of what you are saying. Some cant seem to get their heads around the idea that once you are keeping something in a box and removing natural selection you arnt dealing with wild animals anymore, but rather starting to domesticate them.