Good news! If Bitmain would offer cloud mining on their facilities it might be the first cloudmining which is not a scam. I would trust them at least, because it's hardly they would ruin their great reputation launching a ponzi scheme.
The problem about the cloudmining is not only about trustworthiness and the proof of mining activity, it is also about the ROI, what is the point of making a contract for a year then you will find that your ROI is a year!! You will absolutely make nothing
Also if you joined with a lifetime contract there is another thing that you need to keep in your mind is the maintenance fee which will rape what you earn.
The result after a year will be a joke.
We will see what Bitmain is planning for this center then we will judge if it worth the pain or not