Replying to my own reply... tsk tsk tsk
there's also stuff like this:
http://www.surplussales.com/Relays/rfcoaxialrelays/rfcoax_bnc.html
Some of 'em even work on 48v! :)
Whether addition of a pair of such units results in a net increase or
net decrease in reliability of the system as a whole is left as an
exercise to the reader.
---Rob