I've been monitoring that TG for a few days around poor stationary reception. Haven't heard any of this J unit pursuit stuff while listening or in the recordings the 800 has snagged off the air. Mostly heard name-to-name informal stuff that sounds like operations on the old CID talkgroups on the analog system.
EDIT: and yes, I've had much the same weekday-only experience, though I think my 800 snagged a recording at 0500 off that TG yesterday.