It's gonna happen, trike or not, hill or not, taking the lane or not.

Last year I was in a flat section and had just rounded a corner, taking the lane to try and influence car drivers to only overtake when they can safely do so in an open oncoming lane. Well a truck blew around me and despite the fact that there was perfect visibility around the corner he passed around wide completely into the oncoming lane, as he should of but there was an car coming. Coming very close and this dude not only passed me but STAYED in the left lane as I watched the oncoming car squeal his brakes and have to jink hard to HIS left right into MY lane. I watched from the ditch I pulled into as the car and truck passed each other on the wrong sides and the truck just sort of meandered back into the right lane about 100 feet later. Luckily the "ditch" was extremely shallow and mowed lawn so I didn't lose control and could exit quickly.

It happens, a LOT. Just keep your whits about you and watch out like a hawk, keep the lane as much as possible so that you DO have somewhere to go to, don't allow yourself to be pinned against the curb.

Ride safe friend!