jmk,
There are some payware add-ons that have movin g air bridges. You tune your com 2 radio to a specific freq after you are in position and th bridge comes out. CAn't remember what the add ons are... I think one of them is something like "British Airports" or something like that.
As to pushback tugs and ground support vehicles... look at the website called Aircraft Repaints of New Zealand. They have a fleet of AI planes that have tugs and ground support. It transforms the AI at your airports and makes them busier places.
In the SimV file library is a tug that you can drive around an airport in.

Hope these leads help.
best,
.................john