Hi...
According to the 0.75 sorcecode ICMP is still the default prot used, and the definition of MTR from bitwizards homepage disagress with you:
"mtr combines the functionality of the 'traceroute' and 'ping' programs in a single network diagnostic tool. As mtr starts, it investigates the network connection between the host mtr runs on and a user-specified destination host. After it determines the address of each network hop between the machines, it sends a sequence ICMP ECHO requests to each one to determine the quality of the link to each machine. As it does this, it prints running statistics about each machine. For a preview take a look at the screenshots."
Even if you use UDP/TCP or whatever, the return packet will be ICMP and that will be ratelimited by any carrier worth there salt...
...recent attempts to get mtr working through a cisco fwsm got me sniffing, and yes indeed, icmp is the protocol in play with mtr (both outbound and inbound). Rgs, craig