[SalesForce] How to override a new related list button to redirect to a VF page (custom controller)

I think there are three general approaches you can take here:

1. (Preferred) Use the $Profile global variable, in conjunction with detecting the Record Type either from URL Parameters or from the object' RecordType.Name field, in a giant case statement. For instance, the following page could be used to override the Account object's New action, assuming that there are Account record types and that you are not skipping the Record Type selection screen in your override:

   <apex:page standardController="Account" action="/apex/{!CASE($Profile.Name,
       'System Administrator',
           CASE($CurrentPage.Parameters.Record_Type,
              'Industrial Account','NewIndustrialAccount_SystemAdmin',
              'Education Account','NewEducationAccount_SystemAdmin',
             'Healthcare Account','NewHealthcareAccount_SystemAdmin','DefaultNewAccount_SystemAdmin'
           ),
       'Sales Manager',
           CASE($CurrentPage.Parameters.Record_Type,
              'Industrial Account','NewIndustrialAccount_SalesManager',
              'Education Account','NewEducationAccount_SalesManager',
              'Healthcare Account','NewHealthcareAccount_SalesManager','DefaultNewAccount_SalesManager'
           ),    
       CASE($CurrentPage.Parameters.Record_Type,
          'Industrial Account','NewIndustrialAccount_Default',
          'Education Account','NewEducationAccount_Default',
          'Healthcare Account','NewHealthcareAccount_Default','DefaultNewAccount_SystemAdmin'
       )    
    )}"/>
   

2. (Complicated and probably not worth it) Use the Web Services API's describeLayout call from within JavaScript in a "dispatcher" page to retrieve an object's actual Page Layout Assignments and then use these to redirect to appropriate Visualforce Pages.

3. Use a 3rd party tool like Skuid to manage the creation of custom interfaces to override standard actions --- Skuid's Page Assignments feature is specifically designed to assist in providing this sort of dispatch functionality for custom Visualforce interfaces.

You can add the nooverride parameter to the page to get back to the normal page. Using your example URL:

https://na15.salesforce.com/500/e?nooverride=1&00Ni000000BGRVE=Communications&00Ni000000BGtUJ=Survey&00Ni000000BH0li=General%20Questions&cas8=Low&cas7=Closed&retURL=%2F500%2Fo

If you are using URLFOR, you can also specify TRUE as the fourth parameter to include the nooverride parameter. If you are using a PageReference, you can add it as a parameter:

ref.getParameters().put('nooverride','1');

The value doesn't matter, by the way-- it doesn't have to be 1. It's just a convention that most developers use from what I've observed (because salesforce.com themselves use that value, and people copy examples).

URLFOR has an optional fourth parameter that you can use. This forces the correct parameter for overriding any button override and showing the standard page. Here's an example that uses that (from the comments):

{!URLFOR($Action.Case.NewCase,null,['00Ni000000BGRVE'='Benefits','00Ni000000BGt‌​UJ'='401K','00Ni000000BH0li'='General Questions','cas8'='High','cas7'='Open'],true)}

You can use general formula functions inside the third parameter to include things like TODAY() or BR(). Text concatenation should use the salesforce.com formula syntax: 'Edit ' & Name might render as "Edit John Doe".