Yes, there are many users who have undergone the Paleo diet on Phase 3. I have not done Paleo but I have seen and heard people do it as Phase 3 too demands no starch or sugary foods. Paleo diet seems to fit the bill perfectly as it also recommends clean eating which seems to work in sync with hcg Phase 3.
Paleo diet also seems to target more on low-carb foods which might help while you are dieting but making it a permanent solution might be challenging as you need carb foods as they are fuel to your energy level.
Overall, you can give Paleo diet a shot during phase 3 as long as you are not planning to permanently stick with it.