Hi Thor,
I know the Maine Narrow Gauge has moved Monson #3,
an 18-ton 0-4-4RT, around to many different sites using a tilt-bed trailer as you describe. The move does require additional blocking to fill in the acute angle where the bed contacts the ground/rails, but while its not something you want to do daily, the method works for short wheelbase locomotives.
For the larger locos, like your EFPP #16, or in MNG's case, B&SR #7 and #8, they use the type of trailer where the flat portion of the trailer separates from the yoke. The trailer is split with the flat portion of the trailer facing the locomotive. A temporary track is then constructed on the flat bed. The track on the trailer must usually be built at a slight ascending angle to clear the rear trailer wheels. Then the tractor is backed back in and the trailer is winched up to reconnect to the yoke.
I've posted a link to your note on the WW&F RR web discussion group (www.wwfry.org). I'm sure those guys will be able to give you additional ideas.
The EFPP locos and other equipment are treasures. I wish you and your group every possible success!
Best Regards,
Glenn