Thank you for the spec!
Just an idea: I've seen receivers that communicate with different baud rates on different channels. Do you have tried to communicate with all "well known" baud rates?
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
I've google-translated this document https://m5stack.oss-cn-shenzhen.aliyuncs.com/resource/docs/datasheet/unit/Multimode_satellite_navigation_receiver_cn.pdf
There is description of both textual CAS* and binary CASIC messages and commands.