This needs more data input. Most importantly, speed/PRs for 400 and 1600, not to mention height, weight, and background with running (no high school running vs. moderate mileage program in high school, or a higher mileage background). It all adds up.
Let's assume a decent athlete with a year or two of high school track, but not XC. Currently able to run sub 60 400 off the couch and close to or sub 5 for the mile, on pure hate and promise of free beer.
Using the schedule above (which is kind of absurd), assuming 20-25 miles a week
2 weeks - 18:00
4 weeks - 17:30
6 weeks - 17:20
And they would not improve a whole lot beyond that, without some additional training. Maybe down to 17:00 or a little under, after several months, assuming that they can also run 4:40s or under for the mile.