Some of these tracks are Easter eggs that only play in special circumstances:
-spl-elite4 is used for matches in their Smogon Premier League tournament
-colosseum-miror-b is used if you have two or more Ludicolos on your team
-xd-miror-b is used if you have two or more Lombres, or both a Lombre and a Ludicolo on the same team
-homika-dogars is used if you have a Koffing on your team whose nickname is "Dogars"