Assuming that you are using the Bing Maps Imagery REST service, you will be able to add pushpin based on the URL parameters, see the MSDN: http://msdn.microsoft.com/en-us/library/ff701724.aspx
Here is an sample request that will allow you to add pushpins, take a look at the pp
parameter:
If you are using embedded maps, here is the list of parameters: http://msdn.microsoft.com/en-us/library/ee692180.aspx