Cheers but what deems a new model?
I suppose a MK6 is a bad example to use as it already has DRLS but say the MK6 never had DRLS and then VW introduced the MK7 next year. Is that a new model or still simply a Golf? Same "model" but just revised!
Most mk6 don't have DRL. What they have is the ability to drive with light on. DRL in the meaning of ECE 48 are SEPARATE DRL. Think Audi and Golf R and the latest GTI with LED lights. That's DRL. Also when the dipped beam is on the DRL must not be on. Any car that drives with both (or fogs on top on that) doesn't have DRL legally.
As for the new type - it's the manufacturer’s decision but it is verified by certification bodies and test facilities. Generally new type is a lot of hassle so that decision is not taken lightly. A new type needs to be substantially different than the previous model in regards to safety and environmental items. A new model can be the same type but modified still falling under the same type. Think model year 2010, MY2011 and so on. Subtle differences, engines tweaks, different colours.
Yes, all new types will have to be equipped with DRL. All existing types (certified before Feb 2011) don’t have to adopt DRL ever. But it may be worth it anyway if competitors do that.