According to an internal Apple Retail training document obtained by 9to5Mac, iOS 8 compatible versions of iLife and iWork apps will come pre-installed on 64Gb and 128GB iPhone 6 / 6 Plus devices. These pre-installed apps include iMovie, GarageBand, Keynote, Pages, Numbers, and iTunes U.
Of course customers of 16GB versions of both iPhone 6 and iPhone 6 plus will also have access to these apps for free. However, they will need to download the apps from the App Store manually or via an App Store prompt. The source points out that it is not yet known whether or not GarageBand in-app purchases will also be available at no additional cost.
Last year, Apple had announced that all new iOS devices would be allowed to download iLife and iWork apps for free alongside the release of major updated versions of each app.