Deoxys EX's "Power Connect" Ability refers to "your Team Plasma Pokémon's attacks (excluding Deoxys-EX)". Does that mean to exclude ALL of your Deoxys EX in play, or just one with the "Power Connect" Ability?
It refers to all of your Deoxys EX in play.
Source: Plasma Freeze FAQ (2013-05-16), TPCi Rules Team (2013-05-16)

Relevant cards

Note: All applicable cards may not be listed below.
BW9_111
BW9_53
BWP_BW82
BWP_BW82