The source gives 4 important congregation rules:
• A traveler may follow a resident during the prayer's time; the traveler then completes 4 rak'ahs.
• After the prayer's time has expired, the source does not validate that same traveler-behind-resident arrangement for the missed four-rak'ah prayer.
• A resident may follow a traveler both within the time and in the corresponding missed-prayer case.
• A traveler leading residents should tell them to complete their prayer because the prayer leader is traveling.
According to the preferred view stated here, resident followers completing after the traveler finishes do not recite in those remaining rak'ahs.