The planning ref is PL\1671\13 and you can view it online at
http://countyplanning.dorsetforyou.com/ePlanningOPS/searchPageLoad.doChild Okeford Parish Council have objected strongly to the proposal on the grounds that:
Lamb House Bridge is an extremely useful, natural height restriction for larger vehicles. It is also possible that the Trailway will be diverted on that route and around the back of Bere Marsh Farm, which would avoid crossing a road and going through a farmyard. This will be much safer for the general public and better for the landowner. If the bridge is taken down this option will be lost.
Looking at the photo on the Shillingstone Railway Project's website, it does look like the bridge has taken some almighty wallops from passing vehicles.