3GPP has established a special web page for activities relating to the new SA6 working group that is handling public safety “mission critical applications.”

http://www.3gpp.org/specifications-groups/sa-plenary/sa6-mission-critical-applications

A copyright agreement is now in place that will allow the Open Mobile Alliance (OMA) Push-to-Communicate for Public Safety (PCPS) specifications – based on OMA Push-to-talk over Cellular (PoC) – to be used in 3GPP specifications for mission-critical Push To Talk (MCPTT)

Read more here: http://www.3gpp.org/news-events/partners-news/1676-oma_poc