The reconstruction was probably done from Bach's "Trauer-Ode" (Lass,
Fuerstin, lass noch einen Strahl) BWV 198 / BCG 34. For more information
look into:
G. A. Theill, "Die Markuspassion von Joh. Seb. Bach (BWV 247): Entstehung
- Vergessen - Wiederentdeckung - Rekonstruktion" (Steinfeld, 1981)
The book includes also the facsimile of Trauer-ode. Let me know if you
come across an English translation.
Hope it helps.
Pawel Kotla