Complex sentence: Chiltern Railways commenced driver training on the upgraded line in September 2015 and the line partially reopened on 26 October 2015, with 2 trains per hour running between London Marylebone and Oxford Parkway.
Split into simpler sentences: Chiltern Railways commenced driver training on the upgraded line in September 2015. When services commence in October 2015, Chiltern Railways plans to operate 2 trains per hour between London Marylebone and Oxford Parkway.