Its a generator similar to Eclipse CDT4.
This generator is for eclipse plugin for stm32 microcontrollers at openstm32.org
The .project and .cproject are the same type of XML, but generated specifically for this cross-compiler plugin for stm32.
I have it basically working, meaning the eclipse plugin is able to build the cmake generated project, but the post build steps are given in add_custom_target in cmake file. It should also work for stm32CubeIDE, since that imports these types of projects.