First of for some reason Logitech s left this a mystery...
On their site, the specs say A2DP Bluetooth, so it definitely has BT, and uses this to connect to Iphone etc.
But they also include a dongle for computer usage. But most laptops have BT so why not advertise that you dont even need a dongle???

Are they using propreitary 2.4G for PC, and BT2.4g for Iphones?

absolutely right, tom;
it comes with its own dongle, and its also the 2.4GHz band its using;

but its rather a wifi protocol than a bleutooth protocol i think :D

unless you can find wireless logitec keyboards and other logitec-devices on your cell phone, cause Then I might be wrong. :D

Since when?