I have recently come across an interesting resource which, while dated (published in 1997) offers some clues about how other states, and countries, cope with overcrowding through sentencing strategies.
Sentencing Reform in Overcrowded Times, edited by Michael Tonry, offers a wealth of information on various countries and their sentencing laws. The international comparison shows the trend we already know well: the US has the largest number of prisoners per capita (see the numbers in the World Prison Population List, compiled by Ron Walmsley from King's College London), and has not emphasized, as other countries have, proportionality in sentencing and seeking non-custodial alternatives. The book has short chapters on every country, summarizing its sentencing rules, and pays particular attention to strategies for battling rising imprisonment rates. A non-obvious example is South Africa, who started worrying about overcrowding back in 1976, and made some subtle changes to its sentencing structure, leading to a decrease in overcrowding in general, and to the overrepresentation of Africans in particular (the book estimates that the abolition of Apartheid crimes was only partly responsible for this change).
The U.S. chapters of the book do not include California, which does not have, as we know, sentencing guidelines and commissions. They also tell us something else that we already know - invariably, the introduction of determinate sentencing led to an increase in prison population across the board, particularly when accompanied by Three Strikes laws. But they also tell us that in Minnesota, Oregon, Pennsylvania, and various other states, prison capacity is factored into the sentencing guidelines as a criterion to be weighed in by the judges. There are various forms in which prison capacity is taken into account: several sentencing reforms, taking place in the mid-1990s, added some non-custodial sentences, and in some cases curtailed prisoners of the non-violent kind when scarce prison room was needed to house violent offenders. These strategies are not consensual; as Jeffrey Ulmer shows in his book Social Worlds of Sentencing, DA's officers are usually opposed to taking jail capacity into account, while judges embrace this consideration as a practical one.
Inversely, it is interesting to find out that changes in the opposite direction are also true; that is, enhancing prison capacity leads to an increase in imprisonment rates, as Stewart D'Alessio and Lisa Stolzenberg show in a paper published in Journal of Criminal Justice.
It is interesting to think whether the number of people sentenced to death in CA will increase with the construction of the New Death Row, and with the possible introduction of double-celling; also, when we consider alleviating overcrowding with new prison construction, we should take into account the increase in people sentenced to prison that, according to D'Alessio and Stolzenberg's findings, may follow such a move. It is also worth thinking of the sentencing commission bill, which we haven't heard about in quite a while, and on how a sentencing commission in CA might take prison capacity into account when fixing our broken sentencing policies.