Its a bit more advanced than just a timestamp comparison.
The agent does a hash on the file and the hash is whats stored on the server side. This hash is then compared at regular intervals. Since it is a hash, there is no revision kept of the file itself. Config track will not tell you specifically what changed inside the file however it will notify you that the file has changed.
Not entirely sure about changing the check intervals, likely it can be done though it would require some digging.
It was very helpful. Now I will be able to use this capability properly and explain my boss how it works . As far as changing the collection interval, in case it is that important for our enterprise, I will make my little quest and find it.