If there is a known vulnerability, I'm willing to bet Apple will find it rather quickly. I'd imagine Apple has engineers pouring over the source code now.
In fact the contract they have with the FBI doesn't supply anything that can break into an iOS 9 device so unless they had a separate product line not included in a contract only two months old it's unlikely it was them.
They have allot of turnkey solutions for various markets as mobile forensics is only a part of their portfolio, but quite a few of their forensic services and products are not publicly listed.
*I worked for an Israeli information security firm that is a research partner and service provider for cellebrite.
Years ago, I could never get a good answer from them whether they could extract information from encrypted devices. I guess we now know what the answer is, they can if they really want to.