Gentlemen,
What I'm personally surprised though is why nobody hires people (like us) to develop translators / gateways between those dialects. That's probably a hell lot cheaper than replacing your core network from one vendor with another vendor...
Hm, Consider this: For a network operator, the game is to get as close to 99.999....% uptime as economically possible.
Why? If something breaks, and you can't fix it within the hour, you'll lose your credibility, and your customers will eventually move to another network. So its really all about business continuity, reliability and risk management.