Priority Alpha was meant as a last-resort emergency call, not one that was received every day.
A Priority Alpha message was sent to Jedi Generals Anakin Skywalker and Obi-Wan Kenobi from the Jedi Council. They took it in the Battle Operations Room. It said that Count Dooku and Grievous were heading to Kothlis to take it over. They found that out through the Special Operations Brigade.