Wikipedia states that most modern scholars thus do not consider the events of Matthew 27:53 to be historical. It cites references to them as "pure novelistic motifs," "these events make more theological than historical sense," "the strength of this part of the narrative is atmosphere, not details."
There have been attempts to reconcile this verse with other sources. One proposition is that by the "holy city" Matthew is not referring to Jerusalem, but rather to heaven. The saints thus appeared only in heaven, explaining why no other source makes note of this event. Most scholars reject this understanding, as "holy city" has referred to Jerusalem throughout Matthew's gospel (such as at Matthew 4:5). The theory also fails to explain what is meant when Matthew states they were "seen by many."
Ian Wilson, in Jesus, page 143, says it is probably safest to regard this as a pious embroidery by an author demonstrably over-fond of the miraculous. Thus we should not expect these resurrections to be confirmed in history or in other writings, such as letters or reports from any of the "many" who saw them.