I'm not sure you understand the question. It's not a matter of IP addresses. Protected tweets are not publicly accessible, so it's not a given that intelligence agencies have access to them unless Twitter is providing it to them, or they've hacked into them.

Twitter's privacy policy doesn't actually require a warrant to give up your "private" info (including your protected tweets).

Law and Harm: We may preserve or disclose your information if we believe that it is reasonably necessary to comply with a law, regulation or legal request; to protect the safety of any person; to address fraud, security or technical issues; or to protect Twitter's rights or property.

https://twitter.com/privacy

Yes, but that's a moot point unless one of the following is true:

1) Twitter monitors all tweets itself for any "subversive" content, and then takes the initiative to report that to the appropriate authorities.

2) Twitter gives full access to all tweets to the FBI, regardless of their content, so that the FBI can sift through the data themselves.

1 isn't such a big deal, but 2 certainly is.

I doubt Twitter gives them everything since it's a difficult engineering problem to handle that much data. But I could easily believe the FBI has a list of terms or phrases that Twitter self-monitors for.

Yes it is a given...it's right in Twitter's privacy policy that they will release your private information to the authorities when asked.

Oh..sp332 beat me to it.