CBSubs 1.3.0 RC2 addresses this using the Paypal API for managing subscriptions, but only as far as Paypal supports it: They support it in selected country as an Option for a monthly fee.
The new PayPal settings in CBSubs 1.3.0 RC2 have Paypal API username, password settings and instructions how to setup your paypal account in order for CBSubs to be able to cancel subscriptions automatically.
That service requires a Paypal option (with a monthly fee as far as I understand) and is available in certain countries only.