We have them in Houston but I do not believe that they are the actual recovered bikes that the victims died riding. I think they are just bikes that someone painted white.

Just searched and found, "How to Obtain and Prepare a Bike: We usually get free “junk” bike donations from bike repair shops or local supporters. We strip each bike of non-essential parts (cables, grips, brakes) and recycle them; this makes it easier to paint and also less attractive to thieves. You should probably use a bike that does not have sentimental value because it could be removed."

This is from How To | ghost bikes