Once the Tdd engine is initialized on the Pluto there appears to be no way to get anything but zeros out of the receive buffer.
Example case:
In the Phaser-Control-with-MATLAB repo, running fmcwDemo.m. Once the script gets past line 111 (i.e. bf_TDD.Enable=1) the Pluto will not return anything but a zero (either in the script or through IIO oscilloscope until it has been power cycled. The phaser device behaves normally when running the pluto and phaser from the pi.
PlutoSDR Rev.C (Z7010-AD9363)
v0.39