Ah. I think the problem here is kind of simple -- the FixedTempoEstimator, being a stupid soul, only looks at the start of the audio file and assumes that the remainder is the same in terms of tempo. However, this file (not unusually) has silence at the start, so it's quite lost.
The host would have to feed it a different section of the file in order to get any result -- and this is not something vamp-simple-host can do, though you can do it in Sonic Visualiser with a selection and the "restrict to selection extents" option in the plugin parameters dialog.
This shouldn't be a problem for other plugins, though -- for example, qm-vamp-plugins.so:qm-tempotracker:tempo (as argument to vamp-simple-host) should give you a list of tempo estimates, with a new value each time the tempo tracker thinks the tempo has changed.
It may be worth noting that none of the published tempo trackers is likely to work very well with this particular recording. (Nice recording, by the way.)