You can use tea bags to brew hot and cold tea for the same brewing time and water temperature as loose tea. However, final quality and taste can vary widely.
Portion-sized tea bags often contain fan (small pieces of tea left over after collecting higher grade leaf tea - often these are considered waste product) or dust (fans with very small particles). Traditionally, CTC tea steeps very quickly, so you won't be able to steep a CTC tea bag more than once. You will never be able to extract the flavor and color that you experience with loose leaf tea. Using tea bags can be seen as faster, cleaner and therefore more convenient.
