You have to read the manual of liberate or siliconsmart. there are many engineers employed by companies to do this. as such PD engineers don't need to know ....." the data is generated as the information is not that useful to them. it is detailed and compute intensive task.
some guidelines :
delay: 7input slews and loads used for inverter and delays is calculated for each of them and put in the .lib
power : current is integrated over the rise/fall times and put as energy in the .lib
setup/hold : the data input is swept till it violates the setup and hold times of the flops for each slew in the design.
The slews/loads change depend on the voltage temp etc. there are standard "methodologies" that have been established and the commercial tools use them to generate the data for the .lib.