Channel response/event messages from ANT come under the 0x40 message ID format, which you can find described in the "ANT Message Protocol and Usage" document. The reference code I believe your referring to uses the "MESG_RESPONSE_EVENT_ID" define to filter out these types of messages.
ANT supports both UART and SPI communication. SPI includes both byte-synchronous as well as bit-synchronous communication. That particular set of reference code uses bit-synchronous communication. Under the "ANT+ Embedded Reference Designs" section, those examples use other types of serial such as UART. For more information on the MCU <-> ANT embedded communication, please refer to the "Interfacing with ANT General Purpose Chipsets and Modules" document.
If you look at the main code examples, they show the application code interacting with whole ANT packets, as the serial communication code abstracts most of it away from the application code.
Best regards
