I have a number of treefern mounts and I find them ... unreliable. I think they work fine for plants that would naturally grow on treeferns but are not suitable for most other plants ... at least not under my growing conditions.
For the first few months they hold very little water and are best suited for orchids that like to dry out quickly, but after 6-12 months they start to absorb a lot of water and stay moist for long periods of time, which means they never dry out with my normal regime of watering. I had an Angraecum didierii on one of these and it grew like mad for the first year, then it quickly declined because the mount never dried out fast enough for it. I also mounted 4 phals on large treefern plaques early this year and even though the mounts are in top condition the phals don't seem to like them. The roots grow straight away from them and even when I tie the roots back onto the mount, they still grow away and never attach to them. I have other phals attached to cork and epiweb and their roots stick to their mounts like glue. The only two plants I have that seem happy with their treefern mounts are a masdevallia and a Zygostates lunata. They're growing on old mounts that always stay moist and they seem to like them for now (they have only been growing on them for about 8 months, so it's early days).
I think your Masdevallia is the only plant that would like the treefern in the long run, but you would need to weather it first so that it stays moist as this particular plant would die very quickly if it ever dried out completely.