If the excavator breaks down on a job site does the operator get out, grab a shovel, and start digging?

To any of the people unsure (because like so many people in tech they've probably never worked with or around an excavator) the answer is, "they do not."

Or when it rains, do the farmers keep farming?

A local model would be akin to a smaller and slower excavator, so yeah, grab the Basterd and grind that dirt.

No but seriously, local models can't replace them altogether, but in case of a complete outage and imminence of work that can't be postponed like resolving support tickets, then it'll have to make do without more capable models.