Current ATP instructor here. The tuition reimbursement is actually a great thing. Most of the airlines on the reimbursement side are requiring 2 year contracts.
Make sure that ATP is willing to just do CFI school for you. They stopped doing short programs a few months back because of the demand that they had for the career program. Not a bad decision, IMO. Wasn't for me because I got cornered into only being able to sign with Mesa, so not really a good option. You should have more available to you.
Feel free to private message me with more questions.