Reapplying to a PhD program while attending another one Let's say a person really wants to go to school X for his PhD, but he was not able to get admission in this round of applications. However, he has an offer from another school Y, where a person with strong ties to school X has agreed to be his advisor in case he attends Y. Is there any good strategy that he can use that will help him get into X, if he applies again next year? 

At the same time he would still like to attend Y and do research with said person at Y in case X rejects him again. Applying as a transfer student doesn't seem like a very good option, since transfers happen in graduate school only in very special circumstances. Could applying as a freshman work out? Would admission committees view him more critically if they know he is already a graduate student at another institute?
I was able to transfer from Georgia Tech to MIT after a year. I initially went to GA Tech to study with a famous professor, who, once I got there, said that she was slated to move to Carnegie Mellon in 2 months. Nobody else at GA Tech was doing what I was interested in at the time, so I decided to go through the application process again. I re-used one of my rec writers from my app to GA Tech, and got 2 new rec letters from GA Tech profs I had worked with. I was able to do this because of a great program GA Tech had at the time (I hope they still do), wherein first-years do 3 mini-projects with 3 profs in their first semester. 2 of those profs provided recs, one of which had come from the MIT department I ultimately got accepted to.

To do something like this, you'll want to do the same and hit the ground running at University Y, starting research projects immediately despite your first-year courses. This will give you recs, and also give the admissions committee at X something new to consider.

One tricky thing is if/how to present your intentions to the profs you work with at X. If they know you're planning to jump ship, they'll be less invested in you. It's probably best if you don't come in saying that you'd like to leave for X ASAP.