I am working on adding wide format to our inplant but of course the suits want ROI info and with that come a basket full of questions.
1. Ink yields - 440cc cartridges, 3'x4' full coverage (food photos), photo paper.
How many prints will I get from the cartidges?

Generaly speaking, most all printers will you roughly the same amount of ink for the same amount of coverage for the same amount of area.
The fact is also that the ink yields are entirely dependent upon the coverage, resolution, area of the prints, and the media printed on. Some medias require more ink than others. Be careful when you read the manufacturers claims about RIO and the cost per print... find out what specs they base their estimates on. I've seen one manufacturer claim based on approx 12% ink coverage and another manufacturer base on 32% coverage. Some rips do have the ability to closely estimate the ink usage of a given print.
2. How much do you keep watch of the printer when printing, let's say, 50 prints of the same file? Is there a cut off of how many to run before you do any service?

This depends on how comfortable you become with your printer. How much can you trust it to print flawlessly? I've seen printers print through an entire roll of media without incident yet other jobs seem to have hiccups every other print. I will admit the printers have gotten more reliable the last 6 or 8 years.
3. Time-wise, how long to run those 50 prints at 1200x1200? 54" machine

Depends on the manufacturer and how honest their specs are.
4. Mount and laminate - how much time to mount & laminate those 50 prints?

once you get the hang of it, laminating is fairly easy work and you should be able to keep up with 3 or 4 printers printing speeds.
5. How accurate are the manufacturers specs when it comes to their claims on cost per sq ft?
.... See #1
I'll take answers from any and all. Even if your answer is the same as some one else, give an answer. I need all the help I can get for finding answers.
Thank you!