Waiving Engvall with the intent to send him to BP makes sense to the extent that the $1.1M of cap space you'd gain (basing this on Big L's post earlier) would allow them to keep an extra player on the roster to start the season. If Tsyplakov and others work out, then Engvall spends the season in BP (and maybe gets "Kulemined" next summer?). If not, they just bring Engvall back up. It gives them some flexibility if they need it. Having said all that, my guess is that they keep Engvall on the roster.
It's true that waiving Engvall saves a little over a million - that's slightly more than waiving Wahlstrom or Foudy, but it's not the difference between keeping an extra player on the roster or not.
Let's say right now Sorokin is on the opening day roster with Engvall as the 13th forward and Bolduc as the 7th D. That leaves the team 37.5k above the cap. If instead of Engvall, the 13th forward is Wahlstrom, that clears up another 150k - still, not close to adding another player. A player making the min would bring that to around 400k so still not enough to make a difference on the roster.
If you really believe in the ragtag group of AAAA players as much as Engvall, and want to get his contract off the books you need to trade him to another team - and it's possible it might take a low pick/prospect to do that, as well as getting around his NTC(lol, great contract Lou).
If a team like Columbus took Wahlstrom to take on Engvall's contract (and Engvall waives) we could clear his contract, wash our hands of Wahlstrom, and start the year with some rotation of Gauthier, Foudy, and Fasching for that last 8 minute a game wing spot with Cizikas and Maclean.
In all likelihood though Engvall will be around whether he's in the lineup or not, Fasching will start the year on IR, Wahlstrom and Foudy will be waived, and at least one of them will be claimed.
***also worth noting, if the team plans on starting the year with both Wahlstrom and Engvall on the roster, there will not be enough money for a seventh D man. IMO this greatly decreases Wahlstrom's chances of making the team.***