woooow
My brother just realized he got an EX raid pass and he did only 3 Tier 5 raids. The three times he did them were in the Articuno Day. Kill me.
Answers
Saw in my local discord that an ex-eligible gym in a relatively inactive cell was raided with 9 people (plus they noticed spoofers) a couple days ago.
That night I drove past the gym and there was a level 2 Electabuzz raid. My gf and I each soloed it. We both got Ex invites to that gym today.
Meanwhile, I've done loads of T5 raids at ex eligible gyms in other cells and rarely seem to get passes for them. About 20+ downtown without a single downtown pass. Got 1 pass out of 3 ex-eligible raids when I first started playing again (have been told players without a prior invite are more likely to get one, so makes sense) and my second pass was when I had done 8 ex eligible raids in the week (including Articuno day, this one is tomorrow).
But yea, for many weeks now I've hit a minimum of 3 ex eligible gyms per week and don't get the invite. I've even had a gym I hit trigger, but I didn't get invited to the raid (although more often than not, it's just different gyms in the cell that trigger and I happen to hit the wrong one that week).
Basically - pick your target. If a gym seems easy to trigger, do a low level solo on it when you get the chance and you'll probably score an invite.