I think Re 4/4 IV were never meant for mass-production, but rather test models for the features that were to be implemented on the SBB "Bahn 2000" project (which will be Re 4/4 VI - Re 460).

I am sure Mike C or Lutz can elaborate more...

The Re 4/4IV was commissioned in the early 1980s and the first 4 prototypes were delivered in 1982. The locomotives were accepted by the SBB and were undergoing testing while in normal operation.
The locomotives were painted in four different liveries to assess the public's preference. The Re 4/4IV used thrysistor based technology and had a top speed 20kmh faster than the Re 4/4II.
At the same time as the series was being developed, the SBB continued to receive delivery of the last batches of Re 4/4II, loks 11249-11349 and 11372-11397. At the same time, plans were being developed for new tractive power for the coming Zuerich S-Bahn and for a new high speed locomotive. The Zuerich S-Bahn lok became known as the Re 450 (Re 4/4V) and the high speed locomotive was the Re 460 (Re 4/4VI).
The Re 4/4IV project was abandoned in favor of the last delivery of Re 4/4II, coupled with the planned development of the Re 460 with a max speed of 230kmh. The technology that had been developed for the Re 4/4IV was applied to the Re 450 and the Re 4/4 KTU (Re 456) which went into service with the BT and SZU and later with the VHB-EBT (RM) as well as the HGe 4/4 (narrow gauge) of the Bruenig Bahn and the FO/BVZ.
During the early 1990s, the Re 4/4IV were used by the SBB to determine the choice of pantographs and livery for the Re 460 (Bahn 2000 locomotives).
In 1985, the SOB had acquired 3 Re 4/4III from the SBB to complement the Re 4/4 #41 (1969) in use by the SOB. The Re 4/4III were returned to the SBB in the mid-1990s in exchange for the 4 Re 4/4IV, which was named class Re 446 with the SOB. The Re 4/4IV became surplus with the SBB with the delivery of the first Re 460s in 1992 and the exchange offered the SOB 4 modern locomotives at a very good price. The alternatives were to retain the Re 4/4IIIs or to join with the BT in the procurement of the Re 456. The SOB opted for the less expensive exchange with the SBB.
During their service with the SBB, the Re 4/4IV were mainly based in Lausanne and primarily handled assignments on the Geneva-Brig-Domodossola and Vallorbe-Lausanne-Brig-Domodossola routes. During the first years, the loks also saw use on the main Intercity line Geneva-Bern-Zuerich-St. Gallen.
It was most common to see these loks pulling either SNCF Mistral 69 coaches (the Cisalpin) or FS Gran Comfort (ex-TEE) coaches (the Lemano) on the Rhone valley route. Later, the loks also pulled Intercities like the Jean-Jacques Rousseau, composed of modern Eurofima coaches of the FS and SBB as well as domestic trains made up of the new EWIV coaches.
Today, the Re 4/4IVs are in service with the SOB pulling the Voralpen Express consists, as well as the Gipfeli Express between Einsiedeln and Zuerich-Altstetten and contracted postal trains in Eastern Switzerland. Of the four Re 446, the lok $446 015 was recently returned to service after repairs to damage incurred after an accident.
Maerklin and Roco have previously offered many variants of these loks in SBB and SOB liveries. Lematec has announced a HO scale brass model of this lok for 2009 in both SBB and SOB colors.

More in German here:
http://de.wikipedia.org/wiki/SBB_Re_4/4_IV

Regards

Mike C

Certainly. The SOB and the SBB (Re 460) meet at many places, for instance at Lucerne, Arth-Goldau, Pfaeffikon, St. Gallen, and Romanshorn.

An Re 4/4 IV (now Re 446) is also possible at the head of a post container train, although this is probably not their daily duty.

The SOB has also been contracted to operate fuel trains to Einsiedeln on behalf of the SBB. I don't know if the SOB Loks are added to the train in Pfaeffikon or whether they pull the train all the way from the refinery.
With the lion's share of the Voralpen Express consists being pulled by the Re 456 (91-96), along with SBB Re 4/4II, the SOB Re 446 have been made available for other operations.

www.bahnpics.com has comparatively frequent photos from the SOB, as does www.bahnbilder.ch

Regards

Mike C