The plan was for a three year trial.
In October 2022, the Transport Select Committee accepted that the project had begun, although consent from UNESCO was still required;
link here.
"Electrification works in Fife and South of Forth progressing Forth Bridge to be done at a later phase. Some components will be erected on bridge to monitor performance in advance of permanent installation. Currently going through consultation and planning. MO added that this has to be presented to UNESCO. SL will make planning aware"
Regardless of whether or not it started on time, any trial will not have run the full three years, and therefore will not have reported yet. Additionally, any findings are likely to be commercially sensitive.