I imagine external TLs have their raises prorated depending on how long they've been with the company.
The same applies to internally promoted TLs, but it depends on how long they've been in role for. I know TLs who've had their raises prorated and TLs who've received the percentage they would have gotten as a TM instead.
Prepare for Next is a leadership training program designed to prepare TLs in becoming ETLs. The networking from it is great, as you meet people from around the district, but that's generally it. Someone who has been in it could offer some more insight (there are quite a few on here who have).