Correct. The agreement can't be to divide the workforce between CSX and the B&E because there is no ratified agreement between the ST and CSX yet. Breaking off the B&E employees is a prerequisite for that happening. Once they're gone the process of moving the ST employees to CSX and eventual folding of the ST can happen. Regardless, all the ST employees now work for CSX, it's a company only on paper now.
As I mentioned in the PAS thread now the other unions need to ratify with B&E, but those are usually rubber stamped compared to the BLE.
The new agreements are as you would expect. The ST agreement removes any mention of territory on PAS. The B&E agreement strikes out territory on PAR. Employees will become either B&E or remain ST employees based on the assignment at the time of cutover. They may bump a job or choose to switch railroads prior to the switch over. Each railroad maintains their respective rosters with prior rights. Vacation rights are retained. Etc and so on. No mention of a date yet.