Question: 
Is there a problem in waiting 5 minutes for the Imam after the fixed time of congregation passes?
Answer: حامدا ومصليا ومسلما
There is no problem, however the Imam should not make coming late a habit.
And Allah knows best.
Hazrat Mufti Ahmad Khanpuri Saheb (May Allah preserve him)
Mahmoodul Fataawaa 1/476