Thanks for that link. Even at such low temperatures it is still possible some proportion of the condensed water in the clouds is in liquid form. For instance actual measurements of Polar Stratospheric Clouds on Earth show that liquid
water aerosols with nitric and sulfuric acid can be liquid down to -80 C:

Polar Stratospheric Clouds.
"Type I a (Nitric acid trihydrate particle - NAT)
crystalline particles forming at 195 K,
Type I b (Supercooled ternary solution - STS)
spherical liquid particles forming at 193 K,
Type II (Water ice) ice crystals forming below 188 K."
http://www.iap-kborn.de/optik/psc/psc_e.htm

Balloon-borne measurements of Polar Stratospheric
Clouds.
"First results of in-situ measurements of the chemical
composition of PSCs are presented, which have been
performed over Kiruna, Sweden, in the early morning of
January 25, 1998. PSCs at 21.5 and 23 km and
temperatures between 187 and 192K have been
encountered with a balloon-borne experiment, a
combination of a PSC mass spectrometer and a
backscatter sonde (operated by N. Larsen, Danish
Meteorological Institute, Copenhagen, Denmark) [1]. In
the clouds, a simultaneous increase of condensed
water, nitric acid, and backscatter ratios has been
observed. The measured molar ratios of water to nitric
acid indicate the presence of liquid mixtures of
water, nitric acid, and sulfuric acid, so-called
supercooled ternary solution particles (STS)."
http://www.mpi-hd.mpg.de/mauersberger/schreiner/#Ballon

Because these Earth clouds are stratospheric, they occur at pressures near those on the surface of Mars. Then low lying fogs or clouds on Mars would occur at similar pressures and temperatures to the liquid water containing PSC's on Earth.

Also a recent report suggests some liquid water in clouds could remain down to -140C(!)

New Observations On Properties Of Water
"ScienceDaily (Dec. 13, 2006) — Recent research on the properties of water reveals information relevant for cloud physics and even cryopreservation science.
"Experimental studies conducted by Ph.D. Anatoli Bogdan at the University of Helsinki, Finland, have received broad interest in the scientific world, as the results might have applications even in the cryopreservation of cells and tissues. Bogdan's results show that mixture droplets consisting of sulphuric acid and water can be slowly cooled down to-140 degrees Celsius and then heated again without ice formation."
http://www.sciencedaily.com/releases/2006/12/061213104104.htm

This might make it possible for even Polar Mesopheric Clouds on Earth to contain liquid water. The Aeronomy of Ice in the Mesosphere (AIM) satellite was recently launched to study such clouds. If such clouds are also found to contain some proportion of liquid water, that would greatly increase the range of possibilities for liquid water clouds on Mars.

Also the last statement in that news release you cited is misleading:

"The amount of water in the martian atmosphere varies greatly in space and time," Colaprete observed. Clouds in the atmosphere largely control the amount of water that comes off of the north pole and migrates to the south pole.
"If all the water in the atmosphere were to freeze out to the surface, it would make a layer of ice about one-fifth the thickness of a human hair, according to Colaprete.
"Cloud mass is typically only 10 to 20 percent of the total water content. However, the thin martian atmosphere is much more sensitive/reactive to the influence of these clouds," he said."

Since the water vapor content on Mars is known to be so low that implies that the water content in any cloud must be even lower. But actually it is because overall the cloud cover of the entire planet is relatively low.
But the water content in precipitation clouds can be much higher than the water vapor content in the surrounding area.
For instance during a storm you can have many inches of rainfall or snowfall. But the water vapor content on Earth is at most 5 to 6 precipitable cm, about 2 to 2.5 inches (the amount of water vapor in an atmospheric column if it were condensed.)

Bob Clark