Preview at WWDC likely in June, followed by September launch.
Apple Responds to Questions About Location Tracking and Privacy
As noted by the Los Angeles Times yesterday, the congressmen have published Apple's 13-page response (full-text PDF) submitted last week and explaining the company's policies.
In its response, Apple points out that users have the ability to turn off location services entirely and that users are required to provide explicit authorization to each application that wishes to access their location information. Responding to questions about the information Apple is collecting, the response notes that, in addition to user-initiated location sharing, iOS devices automatically collect information on nearby cell towers and Wi-Fi access points along with GPS locations, batching and encrypting the data before sending it on to Apple via Wi-Fi every twelve hours in order to assist with refinements to Apple's database of fixed access point locations.
Apple also discloses its usage of location information for administering its iAd platform, where GPS coordinates are immediately translated into zip codes for the purposes of serving ads. This information is not, however, passed along to advertisers, and Apple plans to maintain the zip code data on its servers for up to six months to assist with administration of and improvements to the iAd program before aggregating the data for administrative use.