You're misunderstanding how this would work. This is effectively what a hacker would do brute force. You have to generate a hash for each password in your common list, for EACH salt in your user list.

326 million Twitter users x each password in your list.

Really comes down to which hashing function they chose, and how fast it does that calculation.

Something like bcrypt is roughly 100ms per hash, which is a LONG time when you're crunching billions of them.