There is a legal provision for the CPR if the USC or LPR petitioner spouse dies. Conditions will still be lifted.
Matter of ROSE, 25 I&N Dec. 181 (BIA 2010)
http://www.justice.gov/eoir/vll/intdec/vol25/3670.pdf
A conditional permanent resident under section 216(a) of the Immigration and Nationality Act, 8 U.S.C. § 1186a(a) (2006), who is seeking to remove the conditional basis of that status and who has timely filed the petition and appeared for the interview required under section 216(c)(1), does not need a separate section 216(c)(4) hardship waiver if the petitioning spouse died during the 2-year conditional period.
Did they already file the I-751 before the accident? If not, there is another provision for a good faith marriage waiver.
8 CFR § 216.5 Waiver of requirement to file joint petition to remove conditions by alien spouse.
(e) Adjudication of waiver application
(2)
Application for waiver based upon the alien's claim that the marriage was entered into in good faith. In considering whether an alien entered into a qualifying marriage in good faith, the director shall consider evidence relating to the amount of commitment by both parties to the marital relationship. Such evidence may include—
(i) Documentation relating to the degree to which the financial assets and liabilities of the parties were combined;
(ii) Documentation concerning the length of time during which the parties cohabited after the marriage and after the alien obtained permanent residence;
(iii) Birth certificates of children born to the marriage; and
(iv) Other evidence deemed pertinent by the director.
There are additional alternatives available, even to re-file as a widower on an I-360. Hopefully, it won't come to that.
However the individual circumstances happen, in the long run, provided that he has no criminal problems that make him deportable, he will get relief.
Let's just hope that she recovers, instead!