On Delta, no. Active employees go before retired employees, but in the category of active employees everybody is treated equally. There are two priorities for active employees though. S3 is standard and everybody gets unlimited S3s. There are also S2s which place you higher on the list, but everybody only gets 6 of those a year. However within those priorities, employees are organized strictly by date of employment (exact date, not year as some other poster mentioned about another airline) so there is no way to differentiate between a commuting employee and a person going on vacation.

In response to the question about being based somewhere you don't live, that happens all the time in DL. They don't care where you live so long as you show up for work. I know a number of people who live in florida but are based in LAX and commute that regularly.