In contrast, many members were familiar with Sion from its earlier bid.
The trust had rejected an earlier bid of $7.50 a share.
The new offer has a value of about $579 million, compared with $880 million for the earlier bid.
The offer carried a 21 percent premium to an earlier bid.
The offer, which is $10 a share higher than an earlier bid, totals $6.3 billion for the shares not already held.
It rejected an earlier bid of $11 billion from the same suitors two weeks ago.
The purpose of some early bids may be to exchange information rather than to set the final contract.
The revised offer was $4.86 a share in cash, up from an earlier bid of $4.46.
The company had rejected the earlier bid, made two weeks ago.
The earlier bids had all been derided as too low.