When it's a standard (which 3G data is), all companies are allowed to build products based on the standard. They also *must* license the patents at FRAND rates, which they negotiate.
In this case maybe apple offered a penny, which is too low, but motorola were demanding 2.25% of the retail price of an iPhone, which is blatantly unreasonable (see my post below!) What happens if moto refuses to accept a reasonable offer, and demands unreasonable amounts? Both apple + MS have told the courts they want a license, and have offered FRAND rates, but moto are refusing to accept it, and there's plenty of evidence that moto is demanding crazy amounts.
They can't be allowed to stop companies from making phones by using the patent as a 'hold-up' device, that would be market abuse (and they ARE under investigation for anti-trust over this already). Hopefully the ITC will see that. What should happen (and this has already happened in apple v. samsung over the same issue in the netherlands) is that the court says apple must pay moto a FRAND rate, apple pays up and that's that.
Thing is, the FRAND rate for a patent like this is actually very low. If moto wins and apple are forced to pay a FRAND rate, moto probably won't get enough money to pay their legal fees, it's that low. So why are they bothering? They want an import ban so they can force apple (and MS) to give them a license to all of their patents - something MS is demanding money for, and apple are refusing to license because they don't want their stuff copied by android.
Basically, it's a tactical move to get them out of a nasty IP hole that they're in - and it's likely to fail, in which case it will backfire and result in large anti-trust fines.