Ahh, subject to transactions. My favorite way to buy real estate! *Disclaimer: I'm not an attorney nor do I play one on TV, this is solely my opinion having done dozens of subject to, wrap, and owner financed transactions*
First, I believe the trust model is very flawed. This is not a workaround to the due on sale clause. The moment someone else becomes the beneficiary, you're in violation. As I understand it, the exception to a due on sale clause by transferring into a trust is: "a transfer into an inter vivos trust in which the borrower is and remains a beneficiary and which does not relate to a transfer of rights of occupancy in the property"
The moment you are no longer the beneficiary is the moment you're in violation. If the loan gets called because you moved it into a trust - the burden of proof will now fall on the owner to prove they did NOT violate.
Let's just pretend you got summoned to court and had to explain yourself to a judge. Could you convince a competent judge that you structured this transaction for any reason BUT to hide it from the lender? That is intent to deceive and could be considered fraud.
The bigger issue I have with the trust model of taking a property subject to is how it is often taught by the so called experts. If you prepare a trust document for someone other than yourself (aka the seller on a deal you're working on) that's practicing law, the first no-no. Second, you have intent to deceive. Finally, if you sell one of these to a third party (where you're not the original seller) and they default - really bad. Do this a few times and you'll almost certainly have your local attorney general breathing down your neck.
Let's take this one step further - in the example given above you sell your house with the beautiful 2.7% 30 year fixed mortgage to a new buyer by doing a wrap or a straight subject to transaction. Lender calls the loan. Now what? You've sold the house - big mess to refinance as you don't own it. Your buyer will be forced to cash you out OR you must have enough cash to pay off the underlying loan. If you and your buyer know this in full disclosure - great. If not, don't do it.
Now, with that said, I've "violated" the due on sale clause many, many times. However, I do it "openly and notoriously" by recording the warranty deed (or in the case of a VA loan, the agreement for sale/contract for deed). When we record the deed, there is clearly no intent to deceive (the lender). Could the loan get called? Yes. Here's the real question: if the loan gets called, can I handle it by refinancing the property? In my case, this is an easy yes. If it's a "no", you may not want to do a subject to transaction.
So again, my opinion here, but in summary: Subject to transactions are great - but do them knowing full well you are in violation of the due on sale clause and you may someday have the loan called. If you can't easily refinance or this causes you to lose sleep at night, don't do them. That simple.