Yes. It shares everything. Data, minutes, SMSes
My secondary sim has been in a modem for the past 4 years. It uses the data as if the data were coming off the main sim. ie it uses night surfer data after midnight till 4am and anytime data the rest of the time.
There is 1 downside though. If you have a dual sim, you cant data share the conventional way. There was an issue with both being active at the same time but I cant remember exactly what it was. I posted about it a long time ago in this thread.