Will Jeff Buckley even chart on the Hot 100 because it is an old track?

Depends if it was removed from the chart because it was going recurrent [e.g. it was on the chart for a long time, Im not sure of the time period, its a year I think, and never fell below 50]. If not then it will re-chart I think, much like Dixie Chicks Not Ready To Make Nice, which fell off the chart at its normal time of release, but re-entered following its Grammy success.

It also must be repromoted by the label. If it wasn't, it considered to be recurrent!

Yeah, that is how it goes. There is a rule that when a song falls out of top 50 after being there more than 26 weeks it goes recurrent. It can only return if it achieves enough chart points to re-enter the hot 100 inside top 50 AND it is being currently promoted by a label. But even a song that never even spent a week inside hot 100 can become recurrent and therefore cannot chart without being currently promoted by a label. So, therefore it doesn't matter if an older song has ever charted or not, the only thing that matters is that whether it is getting repromoted by the label or not. Dixie Chicks did re-enter because the song was still being promoted by the label into the adult top 40 and adult contemporary charts. I think nowadays the only two ways to have current promo for an older track is either to send it again to some (or multiple) airplay format or/and release it as a physical single again. If neither happens, as the case is with Hallelujah, the song will not re-enter hot 100. Too bad thou, with those kinda sales it would have probably entered at no 6 and based on its I-Tunes success currently it probably will even increase sales for next week's chart.