And is it recruitable
There isn't an actual Lucario in Red and Blue rescue team. Rather, there is a "Easter Egg" featuring it. Once you have achieved the highest rank, the Lucario Rank, you will revive a statue of the Aura Pokemon outside the base of your team. Alakazam will also tell a little story about Lucario and how he wants to become just as great as Lucario was.
The statue is not recruitable btw.
EDIT: Another source: http://bulbapedia.bulbagarden.net/wiki/Team_Base#Figures
No because Pokemon Mystery Dungeon Red/Blue Rescue Team consists of Pokemon from Gens I-III. While Riolu/Lucario is Gen IV.