Subway/Railroad connections?

Where exactly do the subways and local railroads connect? I think MNRR connects in the Bronx and LIRR in brooklyn, but im unsure of exactly where....I know a decade or two ago MNRR was seriously considering using subway shuttles on MNRR track if a major strike went down. I think some of the older digital subway displays have a code to display 'MNRR SHUTTLE' and 'LIRR SHUTTLE' as well.

Thanks for the help guys!