I've just been looking through the Live Object Model reference, and it seems there is no property documented in it to retrieve a clip's tempo. Is this just an omission, or is there really no way to access this parameter?
I don't know if this parameter is available via m4L but I suggest you ask the clip itself with a "getinfo" ( is it the right command ?) to print a listing of all available attributes.
There are some undocumented features afaik.
Anything that shows up in response to a getinfo message that's NOT listed on the refpage for the Live Object Model is an error that ought to be corrected. We already know about playing_position. If you find any more, let us know by all means.