Bibarel gets Baton Pass?
Though no source actually confirms this, it would make sense if it did. Why? Lemme explain.
See. in Gen IV, Simple just doubled the effect of these stat modifiers. So, lets just say he gets Agility, Bibarel's Speed would be at +2, but his Speed would triple, but the cap is still +6 (x4). Also, because of just the modifiers effect being doubled, you could use a move like Defense Curl 6 times without it failing, even though the effect will max out at the third Defense Curl.
Transitioning to Gen V, the stages now double along with the modifier. So now, after an Agility, Bibarel's speed would not only triple, but now your stages go right to +4 meaning it won't work on the third time at all. So now Defense Curl will fail on its fourth try.
Now lets throw in Baton Pass.
See, in Gen IV, if your Gliscor used Agility and then passed it to Bibarel, than Bibarel's speed stage would be at +2, but his speed would triple. In Gen V, if Gliscor were to Agility and BP, then Bibarel's stat stage would be just at +2 and would only have his speed doubled because that is what the modifier is at.
Now if Bibarel were to Agility, his speed stage would be at +4 and if he were to pass that to Gliscor, Gliscor's speed would triple.