The answer is - it depends on the offset.
Because this has personally driven me mental as half the wheel companies don't seem to know the offset, this will hopefully help.
I'm going 10x6 on my Clubman Van (discs and spacered drums) and will be (sort of) fitting them under group 2 arches. But I'm going with split rims so can choose my own offset.
From my research on the 10x6 compared to my Contessas that currently fit (again sort of) without arches and are around a +27 offset. Remember these measurements apply to the wheel only (tyre not accounted for) on my particular Mini with my particular stock wheel arch (they are very slightly rolled).
From biggest 'poke' to smallest:
Genuine Minilite Deep Dish 6x10. -15 offset. Protrude 55mm.
Midland Wheels Mamba 6x10. -7 Offset, protrude 47mm.
Midland Wheels JBW 6x10. -7 Offset, protrude 47mm.
Ultralite 6x10. -3 Offset, protrude 43mm.
Revolite 6x10. +5 Offset, protrude 35mm.
Cosmic 6x10. +6 offset, protrude 34mm.
Starmag 6x10. +7 Offset, protrude 33mm.
Genuine Minilite 6x10 (normal offset). +7 offset, protrude 33mm.
Group 2 arches, depending on who you listen to and where you buy them (and measure them) from, vary from 1.75 inches (44.5mm) to 2.5 inches ((63.6mm).
So the answer as to whether a 10x6 will fit under a group 2 arch or not is more complicated than it may first seem.
Add to this the fact that your tyre choice also makes a difference and you can be pretty confused by it all!
I will measure the tyre width of an AO32Rs on my 10x5s versus 10x6 when they arrive.
Hope that helps. Though it probably just adds to the confusion.