According to the Minister of Makkah:

Sheikh Abdurrahman Sudais is the Chief of imams at Masjid Al Haram.
Sheikh Saoud Shuraim is the Deputy Chief Of Imams Makkah.
The imams have a set Rota to decide who leads which prayer in Makkah.
Fajr duty is given to Sheikh Salih bin Abdullah al Humaid. However, since his appointment as chairman/speaker of the Saudi Parliament, Majlis Shura, he spends most of his time in the capital, Riyadh. In his absence Sheikh Saud Al-Shuraim leads. Sheikh Shuraim If on business, then Sheikh Johany must lead the prayer.
Zuhar is led by Sheikh Usama Khayat.
Asr is led by Sheikh Al-Talib.
Magrib duty is given to Sheikh Sudais, with Sheikh Faisal Gazzawi, Maahir as back-up.
Isha is primarily led by Sheikh Al-Talib, with Sheikh Khalid Al Ghamdi leading in his absence.
Scheikh Johany, Maahir, Ghamdi, Ghazzawi only make representations.