Not to be rude but, no they couldn't, The Spartan I's could not where power armor, as they were like Sgt. Johnson. THey just had slight augments. Therefore the point is moot. :D
Hey look what just came up.
"The Unidentified Lieutenant is a SPARTAN-II Commando of the UNSC Naval Special Warfare Command [1]. He served with Noble Team during the Battle of Reach in 2552."
http://halo.wikia.com/wiki/Unidentified_Lieutenant_(Noble_Team)
Voila
Were not saying he can't be a spartan II, I actually have my money down on him being a Spartan II, albeit a SII mark II, we just pointed out spartans just don't join up to be spartans, it's quite plausible hes just joining noble team.
Yes i see that now, he just pronounced it differently than I imagined. I Thought it was Peh-gus-ee not PegGAHsee.
and Kat appears to have a suped-up halo 2 odst helmet. Oh and how would Jorge no Wolf was on Pegasi if he didn't recognize him...
Exactly, could have been another Pegasi and Spartan-II's (aside Kurt) had no knowledge of Spartan-IIIs...so yeah, my money is on him being a Spartan-II mark II