EPG is SLOW on XC and MAC connections.
XC and MAC connections need to made hundreds (if not thousands of HTTP request to get EPG data).
M3U + XML is super fast to load EPG because it's a single HTTP request, but you lose catchup ability.
Most service providers provide XMLTV URLs for their EPG.
The channel ID's in the XC and MAC API's match the channel ID's in the XMLTV EPG.
It would be reasonable from a technical standpoint to allow XC + MAC connections to use an XMLTV file for EPG instead of the native API. Just add an optional URL field in the portal settings dialog.
I would like to request this feature be added to MyTVOnline.