Availability of transferable residence nil rate band relief and downsizing query

Background:

Husband died having sold his main residence during his lifetime. He did not purchase a replacement property.

His estate passed on IPDI trust to wife (direct descendants thereafter), so no IHT was payable.

Wife owns a property in which she lives. Her estate will pass to her direct descendants on her death and her RNRB will be available.

Question:

When wife dies, can her executors claim any TRNRB/downsizing relief from her late husband’s estate?