Dynamic IPs are indeed more difficult to put on trusted lists. It's not impossible, but it's a lot harder. Most people with dynamic IPs don't send directly today, and they don't host mailing lists. In fact, most ISPs these days have taken to not even letting dynamic IP hosts use port 25, you have to manually ask them to remove the block -- if you can even ask. However, their mail will still work, just through the throttles.

The goal of the plan is for most of the main SMTP servers in the world to join the trusted lists, so that 99% of the non-spam flows peer 2 peer as it should. Then 1% of the real mail, and almost all the spam, goes through the throttle servers.