I am currently helping an occupier create a new flexible working environment by facilitating the change management process to ensure the staff buy-in to the new working arrangements. I presented my usual list of the benefits of flexible working (to both the organisation and the individual) but was told to go away and collate hard evidence. The client is an engineering practice and their staff includes analysts and planners; as a consequence their nature is to challenge and not accept consulting recommendations without detailed and rigorous data to back it up.
Fortunately I have access to case studies that I have collected over the years as a workplace consultant, and I also found quite a few published on the web. You can read through the case studies in my occasional paper on Flexible Working Benefits.