Right from the OMNI-FAQ:
Mr. Pay-Per-View
-Non-superstar-specific High Risk maneuvers cannot be reversed from hand with It’s Great To Be Back Here In…, but non-unique High Risk maneuvers could be reversed from Arsenal by that card.
-If there is at least one card already in hand, a card may be discarded to play Unscripted if Mr. PPV does not have less Pre-match cards in the Ring area than his opponent.
Also, just for future reference:
It’s Great To Be Back Here In…
-This reversal will not ignore restrictions from Enforcer or Superstar Abilities such as Big Freak’n Machine.
-This reversal cannot ignore restrictions from RMS cards such as Atomic Lariat.
-If a restriction exists from an Ability (not a card), Great To Be Back can still reverse from another area if applicable. EXAMPLE: Big Freak’n Machine plays a non-unique maneuver; Great To Be Back cannot be played from hand, however if overturned and no other restrictions exist, it could reverse the maneuver due to BFM’s restriction.
-This card can be played to negate restriction such as Melina: Naughty Manager and The Title Is on the Line!
-If Extreme Warfare is in effect, any non-unique maneuver can be reversed by Great To Be Back when played from hand or overturned (unless another reversal restriction prevents it).