You can achieve this using the Mark Feature of Notepad++ combined with Regex.

First of all, ((?:mcc|mnc): \d.*) will match you all values of mcc and mnc with the following digets.

You can then use Mark feature with Regex to mark all matching rows in your Log.

Afterwards go to Search, Bookmark , Remove Unmarked Lines

Result:

After you've done this you can save the result in another file.