New Yorkers know that a new trend is officially over as soon as it's mentioned in the NY Times. Clearly, I've forgotten this, because I actually believed they were new when the car reviewer said Volvo's integrated booster seats were "a genuine advance." New to him, anyway.
As several readers and the good government types up in Canada City know, Volvo has offered integrated booster seats--and before that, matching booster cushions--since at least the 1996 model year. 
The 1998 850 was the first car mentioned in Transport Canada's official public notice [not a recall, understand] that though Volvo's integrated booster seats were labeled as safe for kids 15 kg and up, Transport Canada only recommends booster seats for kids 18kg and up. And in some "provinces," using a booster seat with an under-18kg kid is actually "illegal." [Bonus datapoint: the notice affected about 14,000 cars, which means around 12-18% of the total units Volvo sold in Canada between 2000 and 2006 had the booster seats.]
Thankfully, the US regulatory agencies are streamlined enough to avoid such petty makework as this. Also, we don't have the metric system, so we don't know what the ($ a 15kg kid is.
 1996 models of the Volvo 850 were originally included in the notice, but were revised out. As it turns out, Volvo has been offering integrated booster seats--and even infant car seats--since 1972, just not in the US. Seems that US regulations require car seats to work in any car, another seemingly logical, yet mutually exclusive, principle. [article sounds like press release at motortrend.com]