You can check to see if info.object matches the name assigned to the cylinder:
Code:
import viz
import vizshape
viz.go()
viz.collision(viz.ON)
dojo = viz.addChild('dojo.osgb')
cylinder = vizshape.addCylinder(pos=[0,1.8,4])
def onCollision(info):
if info.object == cylinder:
print 'Collided with cylinder'
viz.callback(viz.COLLISION_EVENT,onCollision)