Just out of curiousity does anyone know if its at all possible to transfer clients from Authorize.net recurring billing into PayPal recurring or visa versa?

Also, has anyone here had success integrating Google checkout into ModernBill and for recurring billing?

i dont think you can simply import anything in to paypal.
i would send out emails with paypal subscription links instead.
actually you can do a mass money request in paypal. that might work. just copy and paste all your email addresses in to the money request tab.