Thank you for your interest in the Intel RealSense Technology.
We wanted to step in and inform you in regards to your query on "how the trigger signal is aligned to exposure events" , that the output sync pulse can be recognized as the VSYNC pulse of the depth sensor. It outputs 7 lines after the end of exposure. The latest development firmware, v 5.10.3 with support for multi-camera sync is now available for download here (as of August 20, 2018)
I hope this information proves useful, please let me know if there is any further information you require.