How so? Lisi is not on trial for meeting with Ford and exchanging packages. Or drinking in a park. He's on trial for selling drugs to a drycleaner. Ford was not involved in this at all. If Lisi pleads guilty, there is no "evidence" because there is no trial. A guilty plea does not somehow give a stamp of authenticity to the police surveillance document. Lisi might be required to admit he sold the drugs or used extortion to get the video but that's all.
And if Lisi goes to trial, how would he "incriminate" Ford? His interaction with Ford has nothing to do with the current charges against him. It is irrelevant to the trial. It simply was used to get a search warrant (and, quite likely, expose some of the mayor's erratic and possibly criminal behaviour to public scrutiny).
ISTM that there is a lot of wild speculation going on (understandably, given the wild events of the past 8 months) and people are mistakenly assuming that a trial would bring up evidence about Ford and that a non-trial would change the status of the police document from allegations to fact. Neither is true. This is Lisi's trial on narrow charges. He has NOT been charged with drunk driving, peeing in a parking lot, taking drugs, selling drugs to the mayor, showing up drunk in public, etc., etc. The allegations by the police respecting these matters will not be "proven in court" because they will not be brought up as part of the evidence against Lisi's drug dealing in the strip mall nor the extortion respecting the video.
The video may not even be made public at the trial. That's a call for the prosecutor. He/she must prove only that Lisi used extortion/threats to attempt to recovery "a video". The content of the video may not be particularly necessary to reveal to prove extortion. And even if the video is shown, hasn't it already done whatever damage to Ford's repuatation that it's going to do? The video of Ford ranting came and went pretty quickly from the public eye. The sorry truth of the Ford saga is that there are so many shameful, volatile, stupid things he's done that the shock value has worn off.
Unless Lisi helps the police in its investigation of Ford or the police finally uncover sufficient evidence to charge Ford, Lisi's trial/guilty plea will be a big yawn.