We do some tests and its still not really working.
Look here:
2500 BGs = 43x Monocell, 18x Taming Monster, 21x Grimm Reaper, 1x Summon MVP.
1900 BGs = 31 x Monocell, 24x Grimm Reaper, 11x Taming Monster, 0x Summon MVP.
Well in Ebilro, there was a higher chances for doing an Awesome Abra Spawnings.