Valid Apostolic Succession

I apreciate all of your responses to my questions. I have another one.

I was listening to the catholic radiostation last week, and they talked about how the pope celebrated the eucharist with one of the orthodox patriarchs back in 1995.

Given the fact that they celebrated the mass together, doesn't that mean that they both acknowledged each others holy orders (apostolic succession) to be valid?

I am curious what you all think.

Thanks-Jake