I don't think there's anything preventing you from using Services in other (PHP) frameworks, it's just that Symfony2's Dependency Injection Container component

I don't think there's anything preventing you from using Services in other (PHP) frameworks, it's just that Symfony2's Dependency Injection Container component makes it very simple and straight-forward. I think it'd be trivial for other PHP 5.3 compatible frameworks to adopt this component to facilitate using Services themselves.