They haven't updated the esp's yet. When Mustaine got signature pickups it took awhile for them to be in his esp sig line. The pickup is called an emg-alx', it's on the sticker under the pickup and you can see the specs on the emg website (hence having a signature pickup). And yes without any kind of midboost the j50bc sounds terrible, which is why jackson put je1200s in their soloists back then.
I know the sticker says EMG-ALX....I put one in my guitar w/ the ABQ.
Spec wise it is the same as the H2, except for ceramic and steel magnet, where the H2 is just ceramic.
I asked this question on the EMG boards and this is what the site admin said:
http://forum.emgpickups.com/viewtopic.php?f=2&p=5077