LHL's bodyguard has it,LKY,and GCT's bodyguards are also
similarly armed.
Inside the briefcase is a H&K MP5K PDW with 2-3 additional
magazines.The weapon's trigger is linked to the handle of the
brief-case,when the handle is pressed,the MP5K inside will
fire.Ususally for VIP Protection missions,the selector for the
weapon is set to full-automatic.And the user has no real way to aim
the weapon,except to point the weapon in the general direction of
the threat and spray the entire clip.
In the movie AD2000,one of the operators from the Hong Kong
Government Service Unit was seen spraying the threat with automatic
fire before opening the briefcase and removing the MP5k inside
while reloading.Show that the weapon can be removed. 
Hope it answers your question.
