They are not oblivious to what happens in tech.
The firmware are encrypted and protected, it is not so easy, and they would need specialist for this.
It is however much easier to do some social engineering or hire a bosch employee :).
Mercedes, porsche and bosch all have their HQ in Stuttgart, I think it is quite easy for them to know what happens with competitors.
Moreover now with Autosar, they scatter vehicle functionalities through ECUs, with each ECU doing a part of the functionality. It's getting really complex now.
To understand the issue with reverse engineering, one needs to understand that there is no standard in car. Each brand and car has its own communication matrix and electrical architecture, which get periodically overhauled. So even if you manage to identify the meanings of the CAN frames for a make, it is useless for the next generation.
That's why you do not find the communication matrix on internet for recent cars, you only find them somehow for old cars. Also because very few people know how to read CAN network and want to invest timr in this reverse engineering
Some (maybe most?) Mercedes units use a Bosch ECU. I'm pretty sure you can dump the firmware from them and figure out how they work fairly easily?