What exactly are you trying to do? OWA is a way to access an Exchange server using a web interface. Comcast has a web interface, you get to it by clicking on the Mail icon on the Comcast home page. It's not the same design as OWA, but it accomplishes essentially the same thing.
Comcast Business Class customers receive two FREE Microsoft Exchange email accounts. "IF" they choose NOT to have Comcast host their email domain, they would be required to use the firstname.lastname@example.org email addresses.
This would avail Microsoft Outlook 2010 for all registered Comast email licenses. These two Exchange accounts would be able to share contacts, calendars and folders as well as a 10GB (MAX) SharePoint site. Additional email seats/licences are $6.99 per month. Along with the email hosting, business customers receive a three page web site. They can create an entirely new domain or drag an existing domain from another hosting service or migrate an onsite Exchange server over to the Comcast hosted email.
They use a third party soup to nuts email migration provider known as "Mural MaaX"
To get a real good look at these & many other hosted and cloud based offerings go to: