You'll need a SIM card or else the GSM module will not initialize itself to make connections. That's different from having a non-activated SIM card installed.
The SIM card has data that tells the device HOW to connect to a network. That's more than simply passing user authorization data. AN inactive SIM still has data about networks it will connect to, and expired subscriber identification. The ability to place a 9-1-1 call is merely a function of bypassing the subscriber identification aspects and placing the call anyway.
My SIM900 halts and tells me I need to install the SIM card, refusing to do much of anything except respond to a few status commands.