Below is an approximate timeline on how it may go:
10:55 land
11:25 exit immigration
11:45 get to Citygate
{one hour at Citygate}
12:45 leave Citygate
12:55 enter airport
13:15 get to gate

The above assumes that you are not departing/arriving at Gate 69 or other gates at the end of the airport, that immigration lines are short (can take 30mins occassionally), that you get a taxi almost immediately. So, you will have an hour at Citygate. Is that enough time to "do" Citygate?- depends on what you need to do, but I would think it is really a lot of wasted time for no real benefit.