Sqlserver: Get Meta-Info about TRN file
Short answer: you can't. Not with the file only, at least.

Long answer: what you can do is query msdb.dbo.backupset on the source instance to extract this information. The backup start/end date of the previous T-LOG backup is approximately the beginning timestamp of the log records conteined in each .TRN file. The end of the log chain is the backup begin/end date of that .TRN file.