When you use the bridgemodeler in Revit you will most likely think that the design of the piers (and all the other stuff) could deal with a little update.
Select a pier and notice the contextual ribbon with the button edit family.
Go to the family categories and parameters and notice that this is a generic model.
You can substitute piers in your project for other generic model families but, you will loose the instance parameter values. That means you will no longer have the height information and so. (unless you have saved that somewhere)
You can edit an existing pier that came with the extension. Be sure to save it under a new name. If you save it in the same folder, as the other piers that came with the extension, you will be able to select your pier from the drop down list in the extension window.
What is important to know is that the intersection of the reference planes: center (front/back) and center (left/right) and the Ref.level is the point lies on the alignment from Civil 3D. (alignment might not be the correct name here, ofcourse I mean the 3D line that is a result of the horizontal alignment and the vertical Profile)
next time more on parameters used in the bridgemodeler.
In the meantime take a look here, that's where you find al the bridgemodel families on a windows 7 machine. C:\Users\Public\Autodesk\REX\2011.0\Revit\Bridges\Families