No, it is not possible to use variable arguments in EL method expressions, let alone EL functions.
Your best bet is to create multiple different named methods with a different amount of fixed arguments.
public static boolean isValueIn2(Integer value, Integer option1, Integer option2) {}
public static boolean isValueIn3(Integer value, Integer option1, Integer option2, Integer option3) {}
public static boolean isValueIn4(Integer value, Integer option1, Integer option2, Integer option3, Integer option4) {}
// ...
As a dubious alternative, you could pass a commaseparated string and split it inside the method
#{webUtilMB.isValueIn(OtherBean.category.id, '2,3,5')}
or even a string array which is created by fn:split() on a commaseparated string
#{webUtilMB.isValueIn(OtherBean.category.id, fn:split('2,3,5', ','))}
but either way, you’d still need to parse them as integer, or to convert the passed-in integer to string.
In case you’re already on EL 3.0, you could also use the new EL 3.0 collection syntax without the need for the whole EL function.
#{[2,3,5].contains(OtherBean.category.id)}