How long does it take for all the soft tissue to heal after surgery to repair broken tibia plateau?

Depends: This depends on many factors, including the severity of the fracture, the extent and type of surgery that was done, as well as any co-existing medical conditions such as diabetes, smoking, etc. For a healthy patient with no other medical problems, the soft tissues should largely heal within a couple of weeks. Your doctor will likely follow you closely to keep an eye on your healing.