The RFD build version seemed to be punishable, but I didn't get punished every time(not sure if it was surprise or tight window that caused that though). I also felt like I could probably have comboed after on the times I hit, but I wasn't prepared for it, but hitstun seemed significant. I have a more thorough write up of my Black Adam experience in the"what can BA do" thread.
As for EXing the bomb, I noticed I couldn't, but what I never got to trying was doing burn during it's explosion. It indeed didn't go away on hit and saved me from combos from characters without lots of forward movement. Catwoman didn't care all her moves kept pushing me off the bomb.
Edit: after reading Joshs twitter message I think the 3 bolts hes referring to Lightning Strike, its the foot targetting lightning bolt(not Black Magic, the little storm cloud, iirc that one also does 3 hits on hit). I never tried meter burning it(didnt come to mind, it worked just fine normally, its a fantastic projectile). If EX does 3, I am very curious.