There has much talk lately about the cost of SD vs HD programming and how Mediaworks might be saving money by purchasing SD versions rather than HD versions of shows, the SD transmission of House being a cited example.
I posed this question to TV3 via their web site and received a fairly authoritative response which said, TV3 always purchases the HD version of a show (if available) they plan to show in Prime time. The fact that some shows are in SD means they were purchased before they began HD programming which presumably means the current series of House, the current series of CSI Miami (which seems to be last season).
Interestingly, there is a show called Cane which is on late at night which is HD 5.1. However this was a pretty short lived series in the US and I guess procured fairly cheaply to fill in some late night time slot.