i was flying on map and I saw silver BK in 2-6, but i receive some message like "You need to have one silver BK to collect it", the same message that i received when BP put in game red and blue ones. so maybe it will be just by payment and it will also give you hercules. the others give just havocs.
LAST EDIT: New event with silver BK are already online on russian servers: You can receive LF-4, Havoc, Hercules and new designs for citadel, aegis and spearhead and it you can buy just with money, like red/blue ones.
maybe with full extra hp 2 configs for speed full shield on drones emp and instantshield