Current transformer (CT) and potential transformer (PT) grounding
The CT and PT secondary are grounded following the high voltage standards on the high voltage side of the installation. This area inaccessible by uncertified personnel, this grounding may not be removed.


  With this argument, can I short the the secondary sides of current transformer and voltage transformer together on a bus-bar and then ground this bus-bar to create a single grounding point?


You cannot, since you would make a ground loop.
If your meter requires this, you must add additional isolation transformers.