Hey Bob,
Our Events plugins and add-ons themselves do not directly integrate with any specific payment processors. Our plugins integrate with eCommerce plugins like WooCommerce, Easy Digital Downloads, Shopp, etc., and these eCommerce plugins integrate with payment processors on their own.
For example, if you were using the WooCommerce Tickets add-on for Events Calendar Pro, then you could separately go buy and install any WooCommerce payment gateway add-on found here → http://www.woothemes.com/product-category/woocommerce-extensions/payment-gateways/
And the Events functionality would work fine, while WooCommerce itself and the WooCommerce add-ons you choose handle all the payment processing, etc.
I hope that helps, let us know if it does or if you have any other questions/concerns! 🙂
— George