From a bussiness point of view: Rob helped build LP to what they are now. As much as all the other members... So it is very possible he still has his % of the band's profit as part of the agreement to they keep going on. If he were taken down from the contracts and profits, possibily there would be a big sue case involving LP.
Even if MIKE and BRAD are the bosses, which they are, at some point of the LP members career they shared pieces of the whole company. in %.
With that, if you want to still use the LP name/brand, you cant just remove a member of the greement unless he decide to sell his % of the bussiness to someone else or another band member.
So maybe... the band wanted to return and Rob just denied, while Mike or whatever offered him a % of something involving the band just to let them keep playing, etc. That's probably what happened.
This doesn't meam he is still involved producing or touring