ok... there's always 2 sides of the same coin.
You want a private bidding process? Ok sure, but the reason the bids should be made public after a bid has been chosen is for the public to see what their money got them. Did the road made with the bids get washed away? What about the much talked about hospitals how is their foundation stability?
The reason the Africans despots like the Chinese is that they are willing to get into hot zones and organize projects. And not interfere with the domestic policies. Who's going to invest $14 million into the Somali telecommunications?
When you work with the Chinese there's an all around relationship; Political, Economic, and Military. While aid given by Western nations comes through NGOs, China gives it at the State level, maximizing it's interests. I'm not going to care if Save the Children stops their Education program in Angola, if the Chinese government is willing to hand out $24 Billion in aid, all without questions to their usage.
There's enough money to go around and enough to be made, what's it to them if a iPhone made in China will cost 1 cent extra because the local warlord wants a cut? That iPhone is still going to be 7+x cheaper than one made in America.
I'm not bashing China's involvement in Africa, don't get me wrong.
Here's an interesting read, quite neutral from Stratfor:
China's Roar in Africa | Stratfor