Is it common for aircraft tugs to work from under the aircraft? I came across this photo showing a tug attached in a way I have never seen before. I assume it was used to allow the aircraft closer to the terminal.

Did this require special equipment or modifications to the aircraft?

Was it a common practice before terminals were redesigned to accommodate large aircraft and large tugs.


Source: wikipedia.org
Yes, this is a perfectly normal practice, still used, especially for tight spaces, as seen in this video moving a 747 into the hangar for service. And no, it doesn't require any special equipment - the nose gear attachment is designed to be used either way.  

A still from the video: