Edge Touring Plus with trail maps?

I don't own a Touring Plus but I've been looking at them, so I'll offer some thoughts even if they may not directly answer your questions.

The Touring models from Garmin are new/unique in an important way: they come preloaded with OpenStreetMap (OSM) map databases, not the "traditional" Garmin maps. That much is clear. What is unclear, and is unforgivably ambiguous in any Garmin info I can find, is whether the Touring models can still support Garmin format maps on micro SD card, or if they can support Garmin custom maps format.

My fear, although not confirmed, is that the Touring models can ONLY use the OSM maps. If so, that eliminates some useful alternatives for your use case. You would not be able to load true topographic maps, such as those Garmin has available for large portions of the US in both 100k and 25k scale. You would also not be able to load Garmin-compliant custom maps for a specific trail/riding area.

So for your use case (locating yourself in a trail network on the base map) the Touring models may only be as good (or bad) as the OpenStreetMap happens to be for a given riding area. OSM does show some trails. I can see some of the Phil's network in Bend, for example, although none of the trails are named. But in general I don't think OSM is going to be a useful base map for this application.

Websites like Skidmap provide great MTB basemaps but for Garmin it is the custom map format and won't, as far as I know, support the Touring Plus model. Only the 800/810.

My Edge 705 is getting a bit long in the tooth, and was happy to see the introduction of the Touring models, but after looking closely at them, I feel more inclined to get an Edge 800 since they can be had for $280 new and they seem to be more flexible in use than the Touring models.

Update . . .

I called Garmin again to pose this question, patiently waited in their 40 minute queue to talk to a person, and asked if the Touring/TouringPlus models could load City Navigator format maps and custom maps. The support person initially kept saying "they support the same courses and tracks that the 800/810 support" but after persisting for 5 minutes he finally understood I was asking about base maps, not courses/tracks. So then he says "yes, I think they do." He doesn't sound confident. So I ask him to confirm definitively since this will influence my purchase. He puts me on hold, presumably asks someone more knowledgeable, and returns to confirm, yes, for certain, the Touring models can run City Navigator on a micro SD, but not the City Navigator maps from CD/DVD. And they can run custom maps.

I'd still like to hear from someone who actually did this, but assuming its accurate, and assuming you don't care about power sensors or cadence sensors, the Touring models are a decent value.

BTW, westernbikeworks.com has the Touring Plus on sale for $240 this weekend.