The Tracker is fitted as standard, and it will beep irrespective of your subscription. I thought from new I had three years subscription from Maserati, which wasn't the case. I assumed the beeping was the Tracker confirming all was ok. The subscription and service is now run by Vodafone Automotive. I don't have there number to hand, but you can find it from Google.
They will be able to explain the beeping and how the whole system works, and it's actually very sophisticated including if the device is triggered a phone call to the owner, and remote vehicle immobilisation with Police permission to the Vodafone people. All this comes at a price though, I just had to renew my membership - over £300 for twelve months!!
Just to confirm we are talking about the same thing, it's sounds like three faint beeps from the back of the car...