I can see why this might be frustrating. Tables in iWork by default are set to automatically detect the type of text that is entered in each cell. If iWork sees a number (of any type) it converts it a Western character. Luckily it is possible to change this.
Open the inspector and go to the table settings section. Under the table settings section you are presented with two other sections ("Table" and "Format"). Select "Format" and you will see that you can set the "Cell Format" of a table. Select the table in your document and and click on the "Cell Format" drop-down menu. As you will see, the current option is set to "Automatic." Change this to "Text" and you will no longer have the problem of iWork changing your input to Western characters!
Note: You may be forced to manually create and enter the values in the table using the character viewer or copy and paste individual characters from Wikipedia in each cell AFTER initializing the table to have the "Text" cell format. Copying and pasting the entire table from Wikipedia seems to override any initial formatting (in the form of cell format) in iWork.