I believe the S60 is like that in the U.S. - really no room under the trunk floor. I believe there is a sufficiently large "well" under the floor of the xc70 though to hold the "doughnut" spare.Seems to depend on the market and the model year. Some come with a compressor and a can of goo.
It is one of my gripes about the current model XC70. Here in Australia a space-saver (doughnut) spare is standard and is fitted in the well beneath the luggage area floor. However the annoying aspect of this is that a just a tiny bit of pre-thought they could have in fact fitted in a full size spare. There appears to be enough depth (once you remove the shallow tray storage thingy), but just misses out on diameter in the lower part of the wheel well.I believe there is a sufficiently large "well" under the floor of the xc70 though to hold the "doughnut" spare.