I've been looking at this for months. I simply wanted my phone to announce "Bluetooth connected" and then begin playing random songs from my collection.
To date, I have been unsuccessful. Each time I try a new combination of profiles, tasks and actions, the bluetooth handshake is different. I've tried intercepting buttons, using AutoInput, counting button presses and many others methods. All have failed.
I have read the bluetooth headset and AVRCP specs and now I'm thinking Tasker, my car or both are not performing bluetooth handshakes correctly and/or in a timely manner. It's difficult to say since so much of the bluetooth handshaking is 'under the hood'.
Sorry, I have no answers but I share your pain.