Have had a Mainland CM prepaid card for years. No problem receiving SMSs free outside China but had to opt into it somehow. Also have to renew your real-name registration before your original passport expires, and do it the same city/province where you did the original registration.
Note that to do the real-name registration and activate the SIM you'll probably have to go to a customer service centre, not a small shop.
My passport expired but my SIM in China still works. I can still receive SMS outside of China.