Cameras could be built using a single board computer (like the Raspberry Pi Zero, but there are better and cheaper options) plus a USB camera module, and the necessary firmware that could well be just a simple script invoking ffmpeg or similar streaming software; all Open Source.
The hardest part would probably be making an enclosure that is solid enough to withstand being exposed to sun, rain, temperature deltas etc. and remain sealed to protect the electronics.
For example:
https://www.friendlyelec.com/index.php?route=product/product...
https://www.friendlyelec.com/index.php?route=product/product...
https://www.armbian.com/nanopi-duo-2/
Then all video can be collected by applications like Shinobi, Zoneminder, Frigate, etc.
https://zoneminder.com/
https://moeiscool.github.io/Shinobi/
https://frigate.video/
The hardest part would probably be making an enclosure that is solid enough to withstand being exposed to sun, rain, temperature deltas etc. and remain sealed to protect the electronics.