Does anyone know if the type S seats are compatible with the 1999 base TL switch plug?

No they are not. You can get it to work just need to use the existing plugs from your old seats and tap them onto the type s seats. The newer cars have memory control as the 99 doesn’t so less wiring for the 99 so when you do this some wires on the type s seat won’t be used but if done right you’ll have full function moving back, forth, up and down.