Do the high end commercial espresso machines, such as La Marzocco FB 80, have steel boilers? I am curious if these high tier machines avoid using brass and copper.

Generally, yes. The site's search function found Espresso machines with stainless steel boilers by searching on "stainless steel boiler espresso machine" (hint, hint). Not all high-end espresso machines have stainless steel boilers; the Elektra T1, for example, has a copper one.