It rather depends on what you mean by "non standard" (he wrote, not having a Record bandsaw!).
Looking at images from Google, they seem to be the common size of slots for a small bandsaw (i.e. most of them) - probably no wider than 3/8" track (at the top of the T-slot). Mine (a SIP) is much the same, and, although a much smaller saw (12"), it uses exactly the same mitre/crosscutting fence as I can see in the BS 400 pictures. It's almost all Chinese factory output these days!
That's the fence part though - the design of these fences means they can fit any sort of runner underneath and still look much the same. I'm guessing the BS400 runner is actually slightly wider than the one on mine.
I think they don't have table saw slots so that the table can be thinner, lighter weight and use less metal in the casting. Bandsaw tables usually can tilt (i.e. move) - table saws don't have to. The slot on my router table is 3/4" and considerably deeper than the ones on the bandsaw. It's standard on larger table saws, but I'll probably never own one, so all three "table" machines in my small workshop have different-sized slots. I just have to live with it!
Anyway, you're not going to get brilliant mitre precision from a bandsaw, although Steve Maskery gets his big Basato to jump through hoops and sing for its supper. He cuts tenons that work straight off the saw with no further fettling.
As long as you can cut square, that's got to be 90% of all possible uses of the sled/fence. What kills it for mitres is this: as you increase the horizontal mitre angle, the starting position of the fence moves backwards along the slot. I have tried to cut mouldings that way (to minimise tearout, amongst other things, finishing by shooting), and soon find the mitre fence needs to start its travel off the table!
I can see the BS 400 table is a lot bigger than mine, but it's symmetrical (with the blade at the centre, and the slots are proportionately further apart than mine are (I think). So, although you have longer slots, the extra distance from the blade means the problem is much the same as on my smaller saw. "They're all like that, sir." It's the geometry that gets you - Record isn't unique in this!
There is another general issue with those slots, which I've encountered fettling both my bandsaw and my TS 200 table saw (wider slots but similar depth) - the machining isn't very nice, and the inside corners (where the slot is wider at the bottom) are quite rough and sharp. That's OK if running something metal in the track, but wooden runners would probably abrade fairly fast. It's hard to smooth them off (tried several triangular files, which have helped, though).
It does look like a nice saw though - if the price is good, personally I wouldn't hesitate.
HTH,
E.