The word estaba in Spanish means someone or something used to be somewhere. If you say, yo estaba en Zamboanga, it means I was or used to be in Zamboanga.
This is onviously where the Chabacano estaba came from. Estaba in Chabacano means to come from. Here are some examples on how the Chabacano estaba is used:
Chabacano: Donde estaba ese comida?
English: Where did that food come from?
Chabacano: Estaba na mi tata este camisa.
Engish: This shirt came from my dad.
Chabacano: Con quien estaba ese regalo?
English: Who is that gift from?
In some instances though, the way we use the Chabacano estaba somehow looks like the way it used in Spanish. Here some examples:
Chabacano: Donde tu estaba?
English: Where were you? (or where did you go)
Chabacano: Estaba yo na banco.
English: I was at the bank. (or I went to the bank)
Chabacano: Estaba adentro este camisa.
English: This shirt used to be inside.
Chabacano: Estaba, nurse mi nana.
English: My nurse used to be a nurse.
Chabacano: Estaba, na San Roque mi nana ta queda.
English: My mom used to live in San Roque.
In the last two sentences, the word estaba is used to express that something happened a long time ago. Thus if we translate the last sentence, it would be something like: A long time ago, my mom lived in San Roque.