The well-known phrase "it takes two to tango" is really appropriate here. If you stop and think for a minute, it takes more than the wireless operator to turn on their network. It also takes radio transceivers (that can both receive LTE signals and broadcast back to the wireless network towers). What if a radio or TV station announced a new service but there weren't any radios or TVs that could receive the broadcast?
Large infrastructure companies such as Nokia Siemens and Alcatel-Lucent make the "backhaul" equipment that powers the broadcast of LTE signals from cell towers. They have tons of electrical power available in which to send out their signals. On the other hand, notebook computers (and some handhelds such as Verizon's new HTC Thunderbolt) have to receive and then transmit LTE signals on battery power.
I recently talked with Andrew Green, Vice President of Marketing for the Mobile Computing Business Unit at Sierra Wireless, about the challenges to bring LTE wireless modems to market at the same time the wireless operator announces their network. While a number of firms plan to manufacture LTE modems for notebook PCs, Sierra Wireless was one of the first to deliver LTE products to the market and decided to introduce models that would be "backward-compatible" so they could "fall back" on 3G technology if the user was not in an area covered by the new LTE network.