I can't find anything either.
It does make sense that the 'Boys would be looking to acquire a veteran TE in trade. Their current TE depth chart:
- Geoff Swaim, 7th-round 2015
... 9 rec/11 tgts, 94 yds in three seasons
... total career snaps: 398 offense, 261 ST
- Blake Jarwin, UDFA 2017
... active one game, no stats
- Rico Gathers, 6th-round 2016
... didn't play football in HS or college
... no games active, spent 2017 on IR
- Dalton Schultz, rookie, 4th-round 2018
It's possible that one of the local Dallas beat writers drew up a list of veterans TEs that the team might/should try to trade for, and that Allen's name was included on the list.
It seems doubtful to me that the Pats would trade Allen before getting a thorough look at how Niklas, Hollister, Izzo and Wimann actually perform in the offense. So, maybe mid-late Camp ... if it happens.