I thought it was just for this weekend, but sure enough I loaded up Horde tonight and level 1 consisted of 3 Boomers. Level 3 brought out a Gunker and 90% were lambent. Did I mention it is supposedly double XP?
Sandra was playing last night and noticed there were no tickers. Fences were staying up forever. Also at one point there were at least four boomers nearby and they were all shooting at about the same time. It sounded like 'boobooboobooooom!'