The suffixes -(a)bat and -in~-ing are both considered progressive markers here (but see comments on Feature 49 "Tense-aspect systems"). The functional difference between them is not well understood, but -(a)bat is the more frequent and more productive form. Both can be combined in which case -in~-ing precedes -(a)bat.
Source: Angelo et al. 1998
Source: Galmurr and Willika 1996
Source: Hudson 1985: 48
Source: Sandefur 1979: 114