These two codes were in effect before 1975. That is the earliest code book I have.
Article 110-26 used to be 110-16 until 1999 when it was reorganized. The distances in table 110-16 were increased in 1978 and have remained the same through the 2002 code. The words "work space shall be clear and extend from floor or platform to the height required by this section" was added in 1996 to address locating transformers and other equipment above or below disconnects. Sounds like in your case that the transformer located below the disconnects met the code at the time it was installed.
Article 380-8 was 6'-6" before 1975 until it was changed to 6'-7" in 1996. That is measured from the floor or platform to the center of the grip of the operating handle in its highest position (ON). It must also be readily accessible, which means no portable ladders, steps, etc. to reach the handle. This definition has been in the code before 1975. If the transformer is large enough to require a step to reach the handle, this is definitely a code violation. Sounds like the disconnects must be relocated.
I find it amazing that these codes have been around for so long and are some of the most ignored and violated safety codes there is!