Experience from last year: kid took the Jan exam, deadline for school of choice was Mar 1. PCAT results were available to schools on Feb 28.
She didn't get accepted at that time though, for several reasons: 1. she was still three pre-reqs short and couldn't expect to get tem all over the summer, but mostly because of 2. she wasn't a resident of that state (yet) and the last few spots left for that final interview cycle were expected to be given to in-state residents. That could work to your benefit if you're a resident of the state where you're applying (if it's a public university).
She re-applied ED to the same school in August, after having moved to the state so she could become a resident, she completed two of the outstanding pre-reqs (with the third class being taken now, as she's gaining residency status), with her PCAT of 86. Interviewed on a Tuesday, got the acceptance email on Thursday.
So yeah...... the Jan exam can work for schools with March deadlines, but tere are other criteria involved that can hurt or help you. Regardless, I still recommend you take the exam, because you have nothing to lose. If you do well, that's great. If you do poorly, you'll have ample opportunity to re-take the exam for the following year's admission cycles.