I have titled many bikes in TN with this service. The main problem I run into is if the bike has been registered in state in 10 years (They stay in the DMV system for 10 years then get purged). Then when you go say hey I need to register, they say but its already in our system from someone else.
This is when it becomes complicated, but I have learned to just stick to the story of "I do not have any idea why its in your system, must have been sold out of state" in the past 10 years. Then the lady gives you the deer in the headlight look and gets the book for Maine laws and walks around about 10 minutes talking to their supervisors. After 10 minutes or so they come back and say fine give me the money. Then in about 2 weeks you get a title.
If it has never been registered in your state or has not been in last 10 years then its very simple. I have probably done 15 bikes in the last 5 years or so and this system has not failed me yet.
I also live on the border of a Bill of sale state and have some relatives that live there. They will title the bike with just a bill of sale 1983 or older.