A bit on the small side, by my reckoning. The figures that come with it on the other hand are a little squatter than 28mm, but still too big!
I know the scale of these vary wildly, but a couple of years ago I bought 2 '1974 Lesney Matchbox Super Kings' transporter trucks for €1,- a piece at a thrift shop. They're intended for use as generic transporters in my Gerry Anderson UFO project (odd how that's been dormant for years and I realize that I just referenced it for the 3rd time this day...

).
They're a bit cramped for 28mm figures, but still plausible. So perhaps the above vehicles (not all of them, probably) could still be shoehorned into a 28mm role?