I recently required a new-in-box Cargo Express Set #33105.
Imagine my surprise when I opened it up and found this among its contents:
That, dear readers, is a piece of A3 track.
This is my 6th piece of A3 but the first one that I have encountered new in a box. It's part of a starter set and not in a #33323 Middle Straight pack, but close enough (my other five pieces were acquired loose from a seller in Germany in early 2014). Set #33105 doesn't appear in catalogs so I don't know for sure when it was sold, but given that it includes a green battery engine and it came to me with a pair of 1998 catalogs—a foldout and a photobook—I think it's a fair guess that it was produced around that time. This is also the year that A3 was introduced.
I am now curious if there are other starter sets that come with this little gem. I know for a fact that A3 was included in the Network Track Pack #33294, but of course that has the BRIO Network paint theme on it making it a not entirely practical source. If I come across any others that do, I'll be sure to let you know.
EDIT: For the curious, here is the track plan for this set. The A3 piece sits below the Railway Crossing #33388. The gap there is 64mm, and using the A3 piece creates a better fit as well as a slightly wider turn than an A2.