Neat idea! High Efficiency Batteries (TL12) hold 60 points of power per dton, while 10 low berths take 1 power point per round and emergency low berths take 1 power point for 4 berths. A portable system might be somewhere in between and less energy efficient since it's supposedly a single berth per container. Tonnage is 0.5 dtons per standard low berth and 1 dton for an emergency low berth that can hold 4 occupants, if absolutely necessary. So the lifesupport system of emergency berths seems to be quite a bit stronger, which would explain the higher energy comsumption. Also note that standard low berths can be duoble occupied, but this reduces the survival rates drastrically (DM-4 as per the Aslan Hkisyeleaa-class Slaver ship).
This all might boil down to single human being needing a quarter of a displacement ton for cryo berth in an absolute emergency, but more ergonomic set-ups (and thus more economic ones, because they reduce failure rates and hence loss of customers) will use 0.5 dtons for a power consumptions above 0.1 and below 0.25 power points per turn. Since efficiency for a single-berth set-up will be fairly low, 0.2 points of power per turn seems reasonable. That's twice the rate of fully efficiency-geared set-ups, but less than emergency berths. This would leave 0.5 dtons for a TL12 battery, delivering 30 points of power or energy for just about 3 hours. That should enable port crews to detach the containers, ferry them across port through customs and to the next ship, where they are re-attached.
Now to the next question: Is this a viable concept. I think, the form stated above is not one regularly used, no. The reasons being that low-berths how I understand them, are used by passengers that absolutely have to go somewhere, but cannot pay for normal means and choose to gamble their lives on some form of almost last-ditch chance. These biographical next (or: last) steps are rare and difficult to predict, making chains of passages and a logistical system for passengers rather unfeasible. The facts might simply be that the company that owns these containers has too much a hassle to keep track of them and deliver services, where they are needed as to offer them. These containers would be highly specialised and passenger 'streams' might not go equally in both directions or be necessary circular. That leaves the company to retrieve their own low-berth containers from a planet, where desperate souls and their means of travel aggregate.
Now, what I could see is that a company uses this for specialised forms of passengers, e. g. prisoners, forced labourers, indentured servants or outright slaves, or simply corporate low-wage labourers. In these cases, usually several individuals would have to be handled at the same time, allowing for more economic set-ups, e. g. 10 standard low berths and 5 dtons of batteries for a total of 30 hours of energy reserves, leaving ample time for lay-over. This would allow companies to move personnel efficiently and quickly between sites, even allowing for 'in-space transits' from ship to ship by cargo scoops or externally mounted containers.
The standard modular cutter could haul three of these containers at the same time, giving a cutter a capacity of 30 cryo-berthed passengers. Alternatively a 30 dton container could carry 25 dtons of cryo-berths (or 50 people) and hold 5 dtons of batteries for again 300 points of power that last 6 hours, still plenty enough time for lay-over. These 50 persons would make for a nice addition to any personnel needed for basic work, not only manual labour, but also e. g. mercenaries. Take your standard Type-C mercenary cruiser and imagine adding one (or even two) of these modules to bolster your reserves. Contracts would probably include a clause that these cold warriors are on reduced pay until defrosted, at which point they also receive a nice bonus (unless the process goes wrong). Of course, custom and colonial forces might use these containers to ferry prisoners from planetary prisons to off-world labour camps. Rura Penthe comes to mind.
