Transition to What?

In light of today's summit talks between the leaders of several African nations and Zimbabwe, one of the proposals on the table is to form a transitional government between Mugabe's government and the opposition under the leadership of Tsvangirai. Notably absent from the talks is South African President Thabo Mbeki. A transitional/provisional/caretaker government would perform the administration functions of the government while tensions eased and electoral reforms pursued. The main question is, who will oversea the process and will the transitional government yield a free and fair election in the future?