Are you talking about autoformatters like gofmt and its ilk? That won't enforce a consistent approach in Lisp which allows the programmer to infinitely outsmart any tool.
Or if you're talking about written-down guidelines, that can help, for a while. But those morph over time too, and so does the new code but the old code lives on forever. Every time a new CTO/Chief Architect shows up, things change but the existing code doesn't. Since we're on the topic of large companies with decades-old codebases, things have changed many many times and you'll have a very inconsistent mess in your hands. It happens even in fairly rigid languages like Java, I can't imagine what you'd end up with Lisp.
Has there ever even been any Lisp-based company with a 20+ year old codebase where a cast of tens of thousands of developers have worked on it over the years? I can't think of any but maybe I haven't heard of it.
Lisp is awesome for a team of 1 (for about a decade I used to write all my personal use code in Lisp) or maybe a small tighly-knit group. Beyond that, I can't see it working well over the long haul.