Can XBOX360 owners play with PS3 owners play online together?

No.

While PlayStation Network allows some sort of freedom, such as in Unreal Tournament III where PC and PS3 gamers could play together, Xbox Live is a completely closed network.

Nah I Dont think of so, you could play human beings on a xbox with a computer with certian video games, yet while the PS3 and Xbox community merged there could be all this Console wars rubbish, additionally no longer all the video games/downloads ect are compatable with eachother by using fact the xbox is closer to a working laptop or laptop additionally theres the priority with video games. only my opinion

they don't i tried with my cousin and its because ps3 is sony online and 360 in Microsoft hope i helped u

No. They can not play online togehter.

no but i know 360 can with pc,i know mass effect can do that kind of online

hope i helped

In theory yes but in practice no.

no. completely different networks run by completely different companies that don't work together. sorry.

NOOOO!!! MICROSOFT=XBOX.....SONY=PLAYSTATION...Microsoft+sony=no...maybe if they were the same company but thare not