Yeah, it's the Wairarapa club holding a meeting there - the calendar would have been hastily put together as it was only at the start of this season that the NZTAB and HRNZ started to put on Tuesday harness meetings in agreement with a request for the Aussie TABs, as it gives them something to punt on earlier in the day.
As you say, there is another meeting on Thursday - that's a meeting under the auspices of the Manawatu club .
I'd suggest the bigger problem with trying to run the trots at Trentham is the attitude of the thoroughbred racing fraternity. After all, Trentham is the "Champagne Turf" (even when the idiotic track manager overwaters it before the Cup meeting) and they couldn't have the wobblies go around.
Grass track racing is quite popular - often produces big dividends as horses who are unsound often enjoy the soft, less jarring grass surfaces. The meeting at Foxton (Kapiti Coast HRC) was trots-only - it was originally supposed to be at Otaki as per usual, but the gallops club there came up with some rubbish excuse. The track at Motukarara (Banks Peninsula) is grass, and gets used a lot more for trots than gallops, likewise with Methven.
Central Districts harness isn't particularly strong anyway, but that Wairarapa example was just a way to fit a couple into the programme.
On the other hand, Avondale had a dual-code meeting last week, with 10 harness races and six gallops and produced a very good Waitangi Day crowd - the advantage there was that races were only 20 minutes apart, and people love quick fixes nowadays.
I, too, have heard the Wellington GRC was on the lookout, but I don't hold out much hope for them getting up and going with a track in the next couple of years.