...will be possible from 12 December onwards when the regional express line from Frankfurt to Koblenz along the East Rhine Railway will be taken over by VIAS, who procured a fleet of nineteen Stadler FLIRT type EMUs for this purpose. Twelve of these are class 428 sets with four segments, and seven are class 427 sets with only three segments.

At least two VIAS 428s were shuttling around Frankfurt Central Station on trial runs this afternoon, and I could capture set 403 with my camera:

One thing I noticed only on second glance was that the VIAS sets are lacking the aerodynamic shrouding along the edge of the roof, which the SBB FLIRTs do have - as you can see in this photo:

Click.

In addition, they are not fitted with auxiliary buffers, which the SBB sets do have as well.