Bad news-- The Comcast remote is not capable of sending the Scene signals. Here's the explanation: Notice in the PDF file that many Yamaha codes are shown as something like 7A-1C (Main Mute). That's shorthand for 7A85-1CE3, because standard NEC1 coding uses 4 bytes of information with the 2nd and 4th bytes being the binary complement of the 1st and 3rd bytes. (The two bytes add up to 255 or 0xFF.) Actually for sometime now companies have been making the 2nd byte independently variable, and we usually refer to that as a device.subdevice pair. You can see that in the Dock commands for example, where straight NEC1 would have 7F80, but the actual code 7F01 (127.1). The Comcast remote knows about many such device.subdevice setups.

Very recently, Yamaha has started to vary the 4th byte, and the Scene codes use what we terms as NEC1-y1. For these codes the 3rd and 4th bytes add to 127 decimal or 7F hexadecimal. The Comcast remote has no setup codes that send such an IR signal, and so there is no way to use EFCs to get the desired signal.

A learning remote can learn the signals which are present of the OEM remote. Or it is easy to buy a JP1 interface cable to add the NEC1-y1 executor to the Comcast remote.