In the following video, Dan Mumm indicates that the tenor guitar is normally tuned in 5th's CGDA like a viola, but it is adaptable to the background of a player of guitar, banjo, mandolin, or ukulele. For us bari-tone-uke players we could tune it DGBE (or DGBD for Open G tuning).
I have one of these Ibanez Artwood AVT1 tenor "parlour" guitars. Ibanez has paid attention to some finer details as you can see in this video. I have wanted to be able to try out a steel string instrument but I injured my left wrist in a cycling accident many years ago and find that in my few attempts in playing a guitar have triggered some discomfort.
I love the instrument. It takes a bit of play to get used to the steel strings after playing flourocarbon strings. Nylon strings are much softer on the fingers but the steel strings have a bit of punch & twang. The parlour design makes it feel just a step up in body size and the length is 36" vs 30" for the standard bari.
Let me know if you've had any experiences with a tenor guitar in DGBE or in standard tuning. I'd like to hear about your experiences.