They could be very well using the earth's orbit around the sun to get better resolution - two data points from opposite sides of the orbit. What I know is that the largest "virtual" radiotelescope is literally the size of earth. The data points are synced with atomic clocks (or better), and a container of harddrives gets shipped into a datacenter to be ingested. Thats hundreds of streams (one per antenna) of data to be just synced up, before the actual analysis even can begin. (I'm just guessing after this) At this point, you have those hundreds (basically .wav files) lined up at timepoints they were sampled (one sample, one timepoint column). So row by row, so you can begin to sort out signal phase differences between the source rows.

I.e to put it shortly: an image is not taken, it is inferred and computed. Not that you even could in the first place, it's a blackhole after all.