Breaking out from unison to SATB

Of course.

1) Create four instruments (staves). Write one part in one staff. Copy to the three other staves (adjusting the octave where necessary for Tenor and Bass). Write the last three measures with their different notes. This will show four separate parts--four separate staves over the entire piece--each in the voice's correct octave.

2) Create four instruments (staves). Write the unison part. Put nothing in the 2nd, 3rd, and 4th staves until the parts separate. Write the four separate parts for the final measures. Go to Format / Style / Score and check the box for Hide empty staves within systems. This will show one part--in one of the three octaves--until the final system or two, when it will display the four parts (since they now have notes).