so there are some rare intermediate mass black holes but they are rare and far away….

from https://lcogt.net/spacebook/radio-telescopes/

is

R = 2.5 x 10^5 x W/D,

where R is in arcseconds and W (wavelength) and D (baseline) are in meters

W = 1.3mm = 1.3 x 10^-3 M
D = 1.2742 x 10^7 M (diameter of the earth)

R = (2.5 x 1.3/1.2742) x 10^-5
R = 2.551 x 10^-5 arcsec

1 AU = 1.496 x 10^8 km
Black hole diameter = 4.4 x 10^7 km = 2.941 x 10^-1 AU
Black Hole distance = 26000 ly = 7.975 x10^3 parsecs

The apparent angular size of an object is (size in AU)/(distance in pc).
Apparent angular size on the celestial sphere of the black hole is

(2.941 x 10^-1) / (7.975 x 10^3) = 0.3688 x 10^-4
Angular size = 3.688 x 10^-5 arcsec

So in the image formed by the interferometer, the black hole will be on the order of one pixel.

The black hole at the center of our galaxy is ~4million solar masses and is 30,000 ly away. The nearest black hole is hundreds of ly away and will only have a few solar masses…

The black holes at the centers of galaxies are special beasts, most black holes carry only the mass of the star that created them.

What angular resolution to they expect to achieve (I expect they are using interferometric radio astronomy).

A very bold and ambitious project, and a potentially very important one.