In MicroStation XM, annotation scale was extended to cells, meaning that the size of a cell is determined by the Drawing Scale of the model they are placed in.  Let's take a closer look by using MicroStation V8i.

Ensure that the cell model has been enabled to be placed as an annotation cell.  This can be done by opening the cell library, navigating to the Models dialog and simply ticking on the Is Annotation Cell column. 

Set the Desired Drawing scale of the active model by navigating to Settings > Drawing Scale.  Also ensure that the Annotation Scale lock is enabled as shown.  When this lock is on, the drawing scale will be applied to  to a variety of elements including annotation cells.

Attach the cell library to the file, and either activate the desired cell by a double-click or use the Place Active Cell tool.   Place the cell on your drawing.  To test if the annotation scale is being applied to the cells, change the drawing scale as shown below.  In this case, the well symbols, text and pipeline symbols are scaled accordingly.

 communities.bentley.com/.../4130.Tip672.mp4