When you have numerous pieces of equipment along a wall, it is OK for work space to overlap, as long as you have 30" in front of any given piece of equipment, even if it is also in front of its neighbor. If the equipment differs in DEPTH, then one piece can penetrate its neighbor's work space by up to 6". So given a big 12" deep panel next to a little 6" deep panel, that is OK. They can share the working width, with a depth starting from the cover of the 12" deep panel.
What is not OK, is a 10" deep disconnect squeezed between a 24" deep transformer and a wall, if there isn't 30" between the wall and transformer.