do we need to be near ironside prime to retain upgraded status, or do all of her clones sound as signal boosters?
All the clones provide the bonus as well as Ironside herself, although the effect doesn't stack so you still only get the one boost (otherwise by this point you'd be getting +16 for the buff and that'd just be ridiculous.) As long as you're within range (about half a kilometer) of any of the Ironsides you'd still benefit from the effect.
The clones are all exact duplicates of Ironside, with the same skills, traits, abilities, personality, memories, sexual proclivities, strange fascination with Frank Sinatra and everything else which makes her an individual, apart from the fact they're fake copies who only 'live' for a few minutes at a time.
PS: You don't get scantily clad cheerleader robots until the boss fight, so Rocksmith has time to charge up his fireballs and roast them all.