Earlier today, FierceWireless reported that the name of the company has been added to the publicly available code listing for the iPhone's carrier bundles. This list is being used by iTunes and iPhones to identify whether or not a service provider supports a SIM card that Apple has made an agreement with.
Upon looking at the carrier bundles available for the iPhone, you'd find the "Verizon_Comcast_LTE_US" on the list. It also mentions the "Xfinity Mobile" service. This code has been updated and is related on Apple's recent iOS release. The publication was then able to confirm this from two different sources who had expert knowledge on the matter.
It's really no secret that Comcast has plans of entering the wireless mobile industry. With today's update, it looks like Comcast is putting the final touches on the service before it makes the announcement in the next coming months.