I don't have this at the moment.
As a user you can turn the modem off completely, you have to establish the connection again from the beginning.
The network needs to confirm your PSM settings before they are used. So you can request these with AT command, but you cannot set the PSM timers. This is for the R4 modules. It is not everywhere available so not everywhere you can go into PSM mode.
The N2 modules can go into low power mode.
If you require low power, go for now for the N2 modules.
Hope this helpes you.